Polyol ester plasticizers and process of making the same   

FIELD OF THE INVENTION

The invention relates to triglyceride esters based on branched alkyl groups, useful as plasticizers and viscosity depressants for a wide range of resins. The invention further relates to a process for producing polyol ester plasticisers from carboxylic acids having branched alkyl chains, obtained by hydroformylation. The polyol esters may also comprise an aromatic acid group.

BACKGROUND OF THE INVENTION

Plasticizers are incorporated into a resin (usually a plastic or elastomer) to increase the flexibility, workability, or distensibility of the resin. The largest use of plasticizers is in the production of “plasticized” or flexible polyvinyl chloride (PVC) products. Typical uses of plasticized PVC include films, sheets, tubing, coated fabrics, wire and cable insulation and jacketing, toys, flooring materials such as vinyl sheet flooring or vinyl floor tiles, adhesives, sealants, inks, and medical products such as blood bags and tubing, and the like.

Other polymer systems that use small amounts of plasticizers include polyvinyl butyral, acrylic polymers, poly(vinylidene chloride), nylon, polyolefins, polyurethanes, and certain fluoroplastics. Plasticizers can also be used with rubber (although often these materials fall under the definition of extenders for rubber rather than plasticizers). A listing of the major plasticizers and their compatibilities with different polymer systems is provided in “Plasticizers,” A. D. Godwin, in Applied Polymer Science 21st Century, edited by C. D. Craver and C. E. Carraher, Elsevier (2000); pp. 157-175.

Plasticizers can be characterized on the basis of their chemical structure. The most important chemical class of plasticizers is (ortho-)phthalic acid esters, which accounted for about 85% worldwide of PVC plasticizer usage in 2002. However, in the recent past there as been an effort to decrease the use of phthalate esters as plasticizers in PVC, particularly in end uses where the product contacts food, such as bottle cap liners and sealants, medical and food films, or for medical examination gloves, blood bags, and IV delivery systems, flexible tubing, or for toys, and the like. For these and most other uses of plasticized polymer systems, however, a widely accepted substitute for phthalate esters has heretofore not materialized.

One such suggested substitute for phthalates are esters based on cyclohexanoic acid. In the late 1990\'s and early 2000\'s, various compositions based on cyclohexanoate, cyclohexanedioates, and cyclohexanepolyoate esters were said to be useful for a range of goods from semi-rigid to highly flexible materials. See, for instance, WO 99/32427, WO 2004/046078, WO 2003/029339, WO 2004/046078, U.S. Application No. 2006-0247461, and U.S. Pat. No. 7,297,738.

However, one of the problems with plasticizers based on esters of cyclohexanoic acid is processability, particularly the fusion characteristics. When a plasticized product is produced, such as a PVC product, the product should reach a temperature at some point during fabrication at which the polymer crystallites are melted. This is called the fusion temperature. In the case of PVC, depending upon the plasticizer, this temperature generally ranges from 160 to 180° C. Plasticizers which are better solvents for a given polymer will fuse at lower temperatures than those that are poorer solvents. Since many plasticized polymer products, such as flexible PVC products, are produced through continuous processes, those faster or stronger solvating plasticizers will arrive at this fusion temperature faster; hence the development of the descriptor “fast fusing” or “faster fusing”. These same plasticizers are also known as strong solvating plasticizers. For most applications, the plasticizer reference standard is di-2-ethylhexyl phthalate (DEHP) as this plasticizer has been the most widely used plasticizer world wide since it was commercialized in the late 1930\'s. Plasticizers which fuse at lower temperatures than that required for DEHP, at the same concentration in a given polymer system, are considered fast fusing plasticizers. Likewise, plasticizers that fuse at higher temperatures than that required for DEHP, at the same concentration in a given polymer system, are considered “slow fusing” plasticizers.

It has been proven to be particularly difficult to identify, develop and commercialize a widely accepted fast fusing plasticizer substitute for phthalate esters. Fast fusing plasticizers are defined in more detail further in this document.

Fast fusing plasticizers are valued in the production of many flexible articles, particularly flexible PVC articles. See, for instance, U.S. Pat. No. 7,297,728. Fast fusing plasticizers based on non-phthalates are also known. For instance, the present inventors have recently described, along with others, fast fusing plasticizers based on cyclohexanoic acid esters of C4-C7 secondary alcohols (see copending application PCT/US2008/080891, filed Oct. 23, 2008), plasticizers based on cyclohexanoic acid esters of C7-C12 secondary alcohols (see copending application PCT/US2008/080893, filed Oct. 23, 2008), and also coplasticizer systems based on cyclohexanoic acid esters and non-phthalate fast fusing plasticizers. See also U.S. Pat. No. 7,323,588.

Other suggested substitutes for phthalates as plasticisers include esters based on benzoic acid (see, for instance, U.S. Pat. No. 6,740,254 or WO 2006/077131) and polyketones, such as described in U.S. Pat. No. 6,777,514; and also in WO 2008/121847. Epoxidized soybean oil, which has much longer alkyl groups (C16 to C18) has been tried as a plasticizer, but is generally used as a PVC stabilizer. Stabilizers are used in much lower concentrations than plasticizers.

Typically, the best that has been achieved with substitution of the phthalate ester with an alternative material is a flexible PVC article having either reduced performance or poorer processability. Thus, heretofore efforts to make phthalate-free plasticizer systems for PVC have not proven to be entirely satisfactory, and this is still an area of intense research.

Triglycerides produced from branched C6 to C9 acids have been studied in the past, but primarily in other technical fields and the studies have been rather limited in scope. W. Keil, in “Zur Kenntnis der Fette aus Fettsäuren mit ungerader Kohlenstoffatomzahl”, Hoppe-Seyler\'s Zeitschrift fur Physiologische Chemie, vol. 282, 1947, pages 137-142 studied the metabolites of a triglyceride of 2-propyl pentanoic acid and of 3-propyl hexanoic acid when fed to dogs, by urine analysis. A. Aydin et al., in “The synthesis of mono- and triglycerides of branched fatty acids and physical properties of the synthesized glycerides”, Chimica Acta Turcica, vol. 5, 1977, pages 93-101, determined physical properties of 2-ethyl hexanoic acid and of 2-propyl hexanoic acid, and predicted usefulness of such triglycerides in numerous future applications in various fields of industry, more specifically in textile industry as softening material in sanforization, i.e. a mechanical shrinking process for fabrics before these are manufactured into articles such as clothing, in cosmetic formulations and in the food industry.

Polyol esters of branched C6 to C9 acids are known as lubricants and lubricant components. A. D. Godwin et al. in U.S. Pat. No. 6,307,093 disclose in col. 12 as useful in this field the esters of branched C9 acids with pentaerythritol, di(pentaerythritol), tri(pentaerythritol); trimethylolethane, trimethylolpropane, trimethylolbutane, and dimers and trimers thereof, and neopentylglycol.

Plasticizers based on triglycerides have been tried in the past, based on natural triglycerides from various vegetable oils. The alkyl groups on these natural triglycerides are linear, and the products can be incompatible when the alkyl chain is too long.

“Structural Expressions of Long-Chain Esters on Their Plasticizing Behavior in Poly(vinyl Chloride)”, H. K. Shobha and K. Kishore, Macromolecules 1992, 25, 6765-6769, reported the influence of branching and molecular weight in long-chain esters in PVC. Triglycerides (TGE\'s) having linear alkyl groups were studied.

“A Method for Determining compatibility Parameters of Plasticizers for Use in PVC Through Use of Torsional Modulus”, G. R. Riser and W. E. Palm, Polymer Engineering and Science, April 1967, 110-114, also investigate the use of triglycerides and their plasticizing behavior with PVC, including tri-iso-valerin (3-methyl butanoate) triglyceride. It was reported that “these materials have volatilities that are much too high for good long-time permanence”.

Nagai et al. in U.S. Pat. No. 5,248,531, teaches the use of articles comprising vinyl chloride-type resins (among others) using triglyceride compounds as a hemolysis depressant, and also comprising 10 to 45 wt % of plasticizers selected from trialkyl trimellitates, di-normal alkyl phthalates, and tetraalkyl pyromellitates. The alkyl chains of the acid moiety R1-R3 in the structure below, formula (I), are independently an aliphatic hydrocarbon group of 1 to 20 carbon atoms and in embodiments at least one of the alkyl chains is branched. One specific triglyceride disclosed is glyceryl tri-2-ethylhexanoate, having the following formula (I).

Zhou et al. discloses, in U.S. Pat. Nos. 6,652,774; 6,740,254; and 6,811,722; phthalate-free plasticizers comprising a mixture of different triesters of glycerin, formed by a process of esterifying glycerin with a mixture comprising a mixture of alkyl acids and aryl acids. A triglyceride ester produced from a 50/50 mixture of 2-ethyl-hexanoic acid and benzoic acid is exemplified. It was found to be compatible with PVC resin, while glyceryl tribenzoate and glyceryl tri(2-ethyl)hexanoate are stated in paragraph [0020] to be known as being incompatible in such resin.

Nielsen et al., in U.S. Pat. No. 6,734,241, teach a composition comprising a thermoplastic polymer as in formula (I) above, wherein at least one of the R groups is a short alkyl group having from 1-5 carbon atoms and at least one of the R groups is a saturated branched alkyl group having from 9 to 19 carbon atoms and also having a hydrophilic group.

U.S. Pat. No. 6,740,254 mentions plasticizer esters based on C4 and benzoic acids.

However, the prior art has not recognized the advantages of using esters, including triglycerides, based on polyols together with particularly selected branched alkyl acids as plasticizers, and in combination with aryl acids as fast fusing plasticizers. The latter may be used with other slower fusing plasticizers in plastics systems. It was stated already hereinbefore that the TGE of 2-ethyl hexanoic (2EH) acid has a problem of compatibility with PVC. A particular problem with esters from alkyl acids having an ethyl branch on the second carbon is a toxicity concern. An ester, when introduced into a living organism such as a human or an animal, may become at least partly hydrolysed. The ester hydrolysis liberates the acid. When the ester comprises high amounts of the 2-ethyl hexyl moiety on the acid alkyl group, 2-ethyl hexanoic acid is liberated in significant amounts in the living organism, which is undesirable because of the toxicity concern associated with this specific acid (Manninen et al, 1989, Archives of Toxicology 63(2), pages 160-1). This effect may be attributed to the specificity of the ethyl branch on the second carbon, and the concern may therefore also relate to other acids having that branch in that location.

Among the problems presented by the aforementioned triglycerides is they cannot be made conveniently and thus generally are quite expensive and/or are specialty chemicals not suitable as replacements for phthalates from an economic standpoint and/or are not as compatible with the range of polymer systems that phthalates are compatible with, and thus are not viable general purpose replacements for phthalates from a physical property standpoint.

For instance, some synthesis methods involve at least two separate steps, such as where the glycerol is first partially esterified with the C10 to C20 branched chain acyl group and then reacted with acetic acid or acetic anhydride.

Other syntheses involving mixed acid feeds will require addition of a hydrocarbon solvent for azeotropic distillation of the water to drive the esterification reaction to completion (as measured by the hydroxyl number of the ester, which is a measure of the amount of unreacted OH groups), due to the spread in boiling points between the mixed acids. In addition, the use of mixed acid feedstock such as cited in Zhou et al. and in Nielsen et al. can increase the process complexity when recycling unreacted acids.

Triglycerides based on acids derived from natural products will be limited to naturally occurring linear alkyl groups with even carbon numbers, which offer very little flexibility in designing an appropriate plasticizer system for a given polymer system.

Thus what is needed is a method of making a general purpose non-phthalate plasticizer having high throughput and providing a plasticizer having suitable melting or pour point, increased compatibility, good general purpose performance and low temperature properties.

The present inventors have surprisingly discovered that triglyceride and or glycol esters, produced by esterification of glycerol, ethylene glycol or propylene glycol with acids derived from the hydroformylation of olefins and subsequent oxidation of the oxygenate to a branched C6 to C9 acid, provide for polyol esters having appropriately branched alkyl groups for providing compatibility with a wide variety of resins and which are obtainable with a high throughput. Esterification of glycerol using an acid mixture with a narrow carbon number range eliminates many of the aforementioned problems, and enables high yield of the glycerol triesters to be obtained, having low residual hydroxyl numbers.

SUMMARY

The invention is firstly directed to a process for the production of a polyol ester comprising: (i) the formation of at least one branched C6 to C9 aldehyde employing a process comprising a hydroformylation step; (ii) the formation of a branched C6 to C9 acid by oxidizing the branched C6 to C9 aldehyde to the acid or by first hydrogenating the branched C6 to C9 aldehyde to a branched C6 to C9 alcohol and subsequently oxidizing the branched C6 to C9 alcohol to the acid; and (iii) the esterification of the branched C6 to C9 acid with a polyol selected from glycerol, ethylene glycol, propylene glycol and mixtures thereof. The oxidation steps are preferably performed with oxygen and/or air. The branched C6 to C9 aldehyde, and consequently also the branched C6 to C9 alcohol and the C6 to C9 branched acid derived therefrom, is preferably characterised by having an average branching of from 0.5 to 3.0 branches per molecule and at least 10% of the branches being methyl branches.

The polyol esters according to the invention are plasticizers which may have a suitable melting or pour point, increased compatibility, good general purpose performance and low temperature properties. Due to the moderate degree of branching of the alkyl chains, they provide advantages over their unbranched equivalents by a lower plasticizing efficiency, providing an advantage of lower cost and lower weight to the plasticized PVC product, by a higher PVC compatibility and extender tolerance, a slower migration, a greater resistance to chemical hydrolysis and a greater resistance to biodegradation. As compared to their more highly branched equivalents, they provide advantages by a reduced viscosity, also when used in a plastisol, a reduced vapor pressure and hence volatility, an improved cold flex performance, a higher thermo-oxidative stability and an increased photostability.

The process according to the invention, in another embodiment, comprises the addition of an aromatic acid into the esterification step, the aromatic acid being selected from the group consisting of benzoic acid, 2-methyl benzoic acid, 3-methyl benzoic acid, 4-methyl benzoic acid, 4-tert-butyl benzoic acid, or mixtures thereof.

The invention is also directed to the product of the process of the invention, which comprises a triglyceride as represented by the formula (I) above, wherein at least one of the R1, R2, and R3 groups defining the acids in the triglyceride, is independently selected from C4 to C9 alkyl groups, whereby, if at least one of a C4 or a C9 alkyl group is present, this C4 or C9 group is present in a mixture of aliphatic acids, and whereby the mixture of aliphatic acids has an average carbon number of at least 6 and at most 9, with the proviso that the average branching on the alkyl groups of the aliphatic acids is from 0.5 to 3.0 branches per molecule, and wherein at least 10% of the branches on the alkyl groups of the aliphatic acids are methyl branches. In an embodiment, the average branching may range from about 0.6 to about 2.2. In another embodiment, the average branching of the C5 to C8 alkyl groups ranges from about 0.7 to about 1.8, preferably around about 0.8 to about 1.6, more preferably about 1.2 to about 1.4 branches per molecule. In embodiments the average branching will be from about 1.1 to about 1.8. These averages are based on the sum total of alkyl groups on all R1-R3 side chains in all the polyols in the mixture, and are molar averages when determined by 1H-NMR as explained below. They should not include any branching that may be present on the aromatic acid, or the aromatic acid part of the polyol ester, should any such aromatic group be present.

The triglyceride according to the invention may bring special benefits in terms of efficiency, outdoor aging, and low temperature flexibility. In addition, it may be a potential substitute for a phthalate ester plasticisers, and may reduce a toxicity concern attributed to 2-ethyl branching.

The invention is also directed to a composition comprising the product of the process of the invention and a resin.

The invention is still further directed to an article comprising the composition according to the invention.

It is an object of the invention to provide a plasticizer suitable for diverse resins.

It is another object of the invention to provide a high throughput process for producing polyol esters, in particular triglycerides.

It is yet another object of the invention to provide phthalate-free compositions and articles.

These and other objects, features, and advantages will become apparent as reference is made to the following detailed description, preferred embodiments, examples, and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, like reference numerals are used to denote like parts throughout the several views.

FIG. 1 is a schematic representation of a process according to a preferred embodiment of the invention.

DETAILED DESCRIPTION

According to the invention, at least one polyol or triglyceride ester is produced by esterification of one or more branched C6 to C9 acids with glycerol, ethylene glycol, propylene glycol or with mixtures thereof. These polyol esters are useful as plasticizers for plastics. The esters, acids, alcohols and aldehydes in the present invention are typically mixtures of chemical compounds. These compounds may differ in isomer structure and may differ in carbon number. When the products or intermediates in the present invention are characterised that are mixtures, unless stated otherwise it is the average for the mixture that is specified.

In preferred embodiments, the process further comprises providing a higher olefin feed for the hydroformylation step from the dimerization or oligomerization of diverse lower olefin feedstocks, preferably the dimerization of a C3 or C4 feedstock, or a mixture thereof.

In an alternative embodiment, the branched C6 to C9 aldehyde is obtained by aldolisation of at least one C3 to C6 aldehyde as the product of the hydroformylation step, or mixtures thereof. Preferred is the aldolisation of propionaldehyde and a butyraldehyde, which may be isobutanal or n-butanal, to form a branched C7 aldehyde as the basis for the production of the corresponding branched C7 acid.

In this embodiment, the process may further comprise the formation of the C3 to C6 aldehyde by the hydroformylation of ethylene, propylene, a butylene, a pentene, or a mixture thereof.

In another version of this embodiment, one or more C5 aldehydes may be produced by the hydroformylation of a C4 olefin, and part of the C5 aldehyde(s) may be aldolised to form a C10 aldehyde. The C5 and/or the C10 aldehydes may then be converted to their respective C5 and/or C10 acids or acid mixtures. These acids may be used individually or in combination in a mixture of acids containing branched acids and having an average carbon number of at least 6 and at most 9, as the feedstock for a polyol ester according to the invention.

In the specific case of C7 triglycerides, the process of the invention provides, in preferred embodiments, an average branching of about 1.2±0.1, based on the branching in molecules having all C7 acid groups and thus having C6 alkyl chains in each of R1, R2 and R3. In the specific case of C9 triglycerides, the process of the invention provides, in preferred embodiments, an average branching of about 3.0±0.1, based on the branching in molecules having all C9 acid groups and thus having C8 alkyl chains in each of R1, R2 and R3. In a more preferred embodiment, there is a blend of triglycerides having a mixture of C7 and C9 acid groups and thus C6 and C8 alkyl chains on R1, R2 and R3 resulting in an average branching of about 1.6±0.2, preferably 1.6±0.1.

The invention further concerns fast fusing plasticizers based on the esterification of polyols with aliphatic acids, benzoic acids, and mixtures thereof, preferably of mixtures of the branched C6 to C9 acids of the invention with an aryl acid such as benzoic acid or a substituted form thereof. The preferred polyol esters are triglycerides, and glycol esters of ethylene and propylene.

The invention also concerns fast fusing plasticizers based on the esterification of polyols with aliphatic acids, benzoic acids, and mixtures thereof.

The term “fast fusing plasticizer”, as used herein, is defined as follows. Using the solution temperature for the C8 phthalate ester DEHP as the standard, those plasticizers with lower solution temperatures, at a given concentration and for a given polymer system, are described as “fast fusing plasticizers” or faster fusing plasticizers, while those with higher solution temperatures are considered “slow fusing plasticizers” or slower fusing plasticizers. This assumes that the plasticizer in question is the sole plasticizer in the polymer system.

The “solution temperature” is demonstrated through the use of a simple test procedure. In this test, 48 grams of the plasticizer to be tested is mixed with 2 grams of the polymer system, such as PVC resin, at room temperature. The mixture is slowly heated, with stirring, until the PVC resin dissolves. The temperature at which the polymer system, e.g., PVC resin dissolves in the plasticizer is recorded as the “solution temperature”. More specifics of the experimental design are not necessary for one of ordinary skill in the art since the important factor is how the plasticizer performs in the experiment relative to DEHP. Other test procedures that can be used to evaluate fast fusing plasticizers are the hot bench plastisol gelation method and the dynamic mechanical analysis of plastisols, both per se well-known in the art.

The solution temperature testing procedure gives a solution temperature of 120° C. for DEHP. The 1,2-cyclohexanedicarboxylic acid of 2-ethylhexanol has a solution temperature of 130° C. The diisononyl ester of the same acid has a solution temperature of 139° C. and the diisodecyl ester has a solution temperature of 149° C. The C11 ester would have a solution temperature >160° C. Faster fusing plasticizers would have solution temperatures <120° C. by this test method, while slower fusing plasticizers would have solution temperatures >120° C.

Using the hot bench plastisol gelation method, which measures the temperature at which a PVC plastisol begins to gel, DEHP has a gelation temperature of 70° C. The 1,2 cyclohexanedicarboxylic acid of 2-ethylhexanol has a gelation temperature of 73° C. The diisononyl ester of the same acid has a gelation temperature of 78° C. and the diisodecyl ester has a gelation temperature of 87° C. The C11 ester would have a solution temperature >95° C. Using this test method, faster fusing plasticizers would have lower gelation temperatures, typically <70° C., while slower fusing plasticizers would have a higher gelation temperature, typically >70° C.

In preferred embodiments, the fast fusing plasticizers of the invention have both solution temperatures and hot bench gelation temperatures lower than those reported for di-ethylheptyl phthalate (DEHP).

Fast fusing plasticizers according to the invention may be used in the production of diverse articles such as flooring, toys, wall coverings, synthetic leather, carpet backing, and the like.

In preferred embodiment, these fast fusing plasticizers can be used in combination with other plasticizers such as di-isononyl phthalate, C7-C9 alkyl esters of cyclohexanepolycarboxylic acids, various acetylated citrate esters prepared from C4-C9 alcohols, and slow fusing esters based on polyols, to improve processability and appearance through reduced surface blemishes, and improved clarity.

In still more preferred embodiments, fast fusing plasticizers of the invention are used in combination with poorer processing plasticizers such as di-isononyl cyclohexanedicarboxylic acid esters, adipic acid esters of C8 to C10 aliphatic alcohols, polymeric plasticizers based on esters and polyesters of diacids and diols, even di-2-ethyl hexyl terephthalate, to provide a phthalate free product.

In embodiments, these fast fusing plasticizers, with or without the co-plasticizers, can be processed with various plastic systems, such as plastisols and extruded products.

In embodiments one or more of the fast fusing plasticizers based on acid esters of polyols are used in blends with general purpose plasticizers such as di-2-ethylhexyl phthalate (DOP or DEHP), and in other embodiments can be blended with poor processing plasticizer such as adipates, trimellitates, di-isononyl cyclohexanoate, polymeric plasticizers, and terephthalates such as di-2-ethylhexyl terephthalate (DOTP). Blending of different plasticizers is very common in the industry in order to obtain a compromise of properties that are considered advantageous compared to what may be achieved using a single plasticizer.

Fast fusing plasticizers can be prepared by the esterification of polyols such as glycerol, neopentyl glycol, trimethylol propane and pentaerythriol with a mixture of shorter chain C4-C9 aliphatic acids, aryl acids such as benzoic acid, and mixtures thereof. When aliphatic acids having C8+chains, such as C9 or C10 acids, it is preferred to use these in admixture with an aryl acid. This improves the compatibility of the plasticiser with the resin.

For example the plasticizer of this invention prepared by the esterification of glycerol can be represented by the averaged formula:

CH2(OOR1)CH(OOR2)CH2(OOR3)

Where for R1, R2, and R3, all three may be the same or different, or two of these may be different from the third. Each of these R groups will contain about 5, 6, 7, 8, 9 or 10 carbon atoms, with at least one of the R groups being branched alkyl and at least one possibly being aryl. In the case of the fast fusing plasticizers of this invention prepared from the esterification of glycerol with isoheptanoic acid as a branched C7 acid mixture, and benzoic acid, the resulting product will be a mixture of isomers according to glyceryl (1,3)-bisisoheptanoate benzoate, glyceryl (1,2)-bisisoheptanoate benzoate, glyceryl (1,2)-bisbenzoate isoheptanoate, glyceryl (1,3)-bisbenzoate isoheptanoate, glyceryl (1,2,3)-trisisoheptanoate, and glyceryl (1,2,3)-trisbenzoate. If a fast fusing plasticizer is prepared by the esterification of glycerol with a mixture of C6 and C7 aliphatic acids and benzoic acid, the number of possible isomers increases even further. In order to obtain the fast fusing properties required for that embodiment of this invention, the molar ratio of benzoic acid to C6 to C9 aliphatic acids needs be at least 1 to 8, more preferably at least 1 to 5, even more preferably at least 1:2, even more preferably 1:1. Although benzoic acid is the preferred aromatic acid, other aromatic acids such as 2-methyl benzoic acid, 3-methyl benzoic acid, 4-methyl benzoic acid, and 4-tert-butyl benzoic acid can be used.

The fast fusing plasticizers based on polyols esters of C4-C8 acids and/or benzoic acid may be supplemented with other fast fusing plasticizers such as hydrogenated forms of butyl benzyl phthalate (BBP), diisoheptyl phthalate, dihexyl phthalate, and dibutyl phthalate, and also dibutyl terephthalate, dibenzoate esters of diethylene glycol or dipropylene glycol, benzoate esters of C8 or C9 or C10 branched primary alcohols, various alkyl sulfonic acid esters of phenol, cyclohexanediacid esters of C4-C7 aliphatic secondary alcohols, acetyl tributyl citrate, acetyl trihexyl citrate, acetyl tripentyl citrate, acetyl triisopentyl citrate, and butyrl tributyl citrate.

Although the preferred plasticizer system of the invention is phthalate-free, in some cases it may be suitable to include certain amounts of phthalates, such as fast fusing plasticizers selected from butyl benzyl phthalate (BBP), diisoheptyl phthalate, dihexyl phthalate, dibutyl phthalate, and mixtures thereof.

In preferred embodiment, these fast fusing plasticizers can be used in combination with other plasticizers such as di-isononyl phthalate (DINP), di-isodecyl phthalate (DIDP), di-2-propyl heptyl phthalate (DPHP), di-2-ethylhexyl terephthalate (DOTP), di-isononyl cyclohexanedicarboxylic acid ester, acetylated citrate esters of C4, C5, C6, C8, or C9 aliphatic alcohols, and slower fusing esters based on polyols, to improve processability and appearance through reduced surface blemishes and improved clarity.

In still more preferred embodiments, fast fusing plasticizers of the invention are used in combination with poorer processing non-phthalate plasticizers such as di-isononyl cyclohexandioates, adipate esters, polymeric plasticizers, even di-2-ethylhexyl terephthalate, which, in preferred embodiments, provides a phthalate free product, which is the term used for products that are at least free of ortho-phthalates, i.e. in which the presence of ortho-phthalate esters is insignificant, such as at most 0.1% by weight, preferably at most 100 ppm by weight. More preferably, the products are also free of other phthalate esters, such as isophthalate or terephthalate esters.

In embodiments, these fast fusing plasticizers, with or without the co-plasticizers, can be processed with various plastic systems using plastisols, extruded products, coated fabrics, injection molded products, and products made through rotational molding.

Fast fusing plasticizers according to the invention may be used in the production of diverse articles such as flexible vinyl resilient flooring, toys, carpet tiles, shoes, chair mats, synthetic leather, wall paper, floor mats, road cones, tubing, and table cloths. In preferred embodiments, one or more of the fast fusing plasticizers is most commonly used in blends with general purpose plasticizers such as DEHP (di-2-ethylhexyl phthalate), DINP (di-isononyl phthalate), or DIDP (di-isodecyl phthalate). But the use of fast fusing plasticizers can be used to improve the processability of any poor processing plasticizer such as adipates, trimellitates, di-cyclohexanoates such as di-isononyl cyclohexanoate, polymerics, and DOTP.

By “short chain aliphatic acids” is meant straight or branched aliphatic acids containing C4 to C9 carbon atoms (including the carboxylic acid carbon), preferably C6-C9 acids, and mixtures thereof, preferably straight or branched chain C6-C8 carbon atoms, more preferably C7-C8 carbon atoms.

In embodiments, plasticizing systems of the invention may be essentially phthalate-free, meaning there may be some inevitable impurity of phthalates due to the process by which the esters are made (such as when the plasticizing system includes, in addition to the fast fusing plasticizers based on one or more acid esters of polyols with short chain aliphatic acids, benzoic acid, or mixtures thereof, also one or more cyclohexanecarboxylic acid esters, which may be made, for instance, by hydrogenation of a phthalic acid analog before esterification or a phthalate ester analog after esterification, and in which traces of the phthalate ester may be remaining) or the system may be completely free of phthalates, meaning that the composition consists of no phthalates, to the extent this can be determined by available technology.

In embodiments, there is also a composition comprising a plasticizable polymer and a plasticizing system comprising at least one ester of a polyol, whereby this polyol ester may be with short chain aliphatic acids, benzoic acid, and mixtures thereof, with or without a slower fusing plasticizer.

In preferred embodiments, the polymers may be selected from any known plasticizable polymer, preferably PVC, polyvinyl butyrals, polystyrenes, polyurethanes, acrylics, brominated rubbers, chlorinated rubbers, and polyolefins. Preferred polyolefins include polypropylene, EDPM, thermoplastic vulcanizates and thermoplastic elastomers.

In embodiments, the compositions including said plasticizable polymer comprise a plasticizing amount of said plasticizing system. The term “plasticizing amount” means an amount sufficient for the purpose of processing the polymer into a final article (such as a toy) or intermediate article (such as a pellet or powder) or the amount of plasticizer required to provide the finished article with the desired amount of softness or flexibility. One of skill in the art in possession of the present disclosure may determine the appropriate amount without more than routine experimentation. Minimum and maximum amounts suitable will vary depending on the plasticizer system, polymerizable polymer(s), additives, and process selected, among other reasons.

The plasticizer system may comprise one or more fast fusing plasticizers based on polyols and one or more slow fusing plasticizers. The terms “fast fusing plasticizer” and “slow fusing plasticizer” have been defined above. The fast fusing plasticizer may be used in amounts greater than or less than the total concentration of the slower fusing plasticizer.

The relative proportions of the plasticizers that are used will depend upon the desired properties of the processing and the final product. In embodiments, it is preferred to use at least 5 wt %, in other embodiments at least 10 wt %, in other embodiments at least 15 wt %, in other embodiments at least 20 wt %, in other embodiments at least 25 wt %, in other embodiments at least 30 wt %, in other embodiments at least 35 wt %, in other embodiments at least 40 wt %, in other embodiments at least 45 wt %, in other embodiments at least 50 wt %, in other embodiments at least 55 wt %, in other embodiments at least 60 wt %, in other embodiments at least 65 wt %, in other embodiments at least 70 wt %, in other embodiments at least 75 wt %, in other embodiments at least 80 wt %, in other embodiments at least 85 wt %, in other embodiments at least 90 wt %, of the plasticizer(s) of the invention, based on the total weight of plasticizer present. The remainder of the plasticizer system may preferably be the at least one slow fusing plasticizer, although other plasticizers may be included, such as other slow fusing plasticizers such as di-isononyl cyclohexandioates and/or even traditional phthalic acid ester plasticizers.

In embodiments, the plasticizer system may comprise no more than 95 wt % slow fusing plasticizer, in other embodiments no more than 90 wt %, or in other embodiments no more than 85 wt %, or in other embodiments no more than 80 wt %, or in other embodiments no more than 75 wt %, or in other embodiments no more than 70 wt %, or in other embodiments no more than 65 wt %, or in other embodiments no more than 60 wt %, or in other embodiments no more than 55 wt %, or in other embodiments no more than 50 wt %, or in other embodiments no more than 45 wt %, or in other embodiments no more than 40 wt %, or in other embodiments no more than 35 wt % or in other embodiments no more than 30 wt %, or in other embodiments no more than 25 wt %, or in other embodiments no more than 20 wt %. In embodiments, it is preferred to use at least 5 wt % of the slow fusing plasticizer, however in other embodiment preferred ranges include between 0.01 and 95 wt %, more preferably 5 to 90 wt %, in other embodiments 10 to 80 wt %, in other embodiments 20 to 70 wt %, in other embodiments 30 to 60 wt %. The fast fusing plasticizers may be present in these same percentages, e.g., 0.01 and 95 wt %, in other embodiments 5 to 90 wt %, in other embodiments 10 to 80 wt %, in other embodiments 20 to 70 wt %, or in other embodiments 30 to 60 wt %. DEHP (which, being the standard, is neither a fast nor a slow fusing plasticizer) may be used, along with phthalate ester plasticizer, and also more than one slow fusing plasticizers may be used.

In the plasticizer system comprising one or more fast fusing plasticizers based on the polyol esters of the invention and one or more slow fusing plasticizers, the slow fusing plasticizers are selected from esters of cyclohexanecarboxylic acids, preferably cyclohexanecarboxylic acid esters of C8 to C11 aliphatic alcohols, more preferably cyclohexanedicarboxylic acid esters of C8 to C11 aliphatic alcohols, which in embodiments will be C8-C11 aliphatic primary alcohols, more preferably 1,2-cyclohexanedicarboxylic acid esters of C8 to C11 aliphatic alcohols, more preferably 1,2 cyclohexanedicarboxylic acid esters of isononanol.

The term “cyclohexanecarboxylic acid” (as used herein) is intended to include the cyclohexane group having at least two carboxylic acid functional groups attached directly to the C6 ring, thus including dicarboxylic acid, tricarboxylic acids, and so on. All possible isomers of polycarboxylic acids are envisioned to be useful, however in preferred embodiments, the dicarboxylic acid isomer with the carboxylic acid groups in the 1,2-substitution position is the preferred isomer. Mixtures of isomers are also envisioned.

Note that cyclohexanecarboxylic acid esters may also be referred to as hexahydrophthalate esters.

The acid moiety of the fast fusing plasticizers of the present invention based on polyols are, as mentioned, short chain aliphatics, preferably C4-C9 acids but more preferably C6-C8 acids, which may be straight or preferably branched or a mixture thereof, and/or benzoic acid or derivatives thereof.

Blends of branched and linear acids, such as mixtures of C6 and C7 acids, each independently selected from branched and/or linear acids, or C7 and C8 acids, each independently selected from branched and/or linear alcohols, or C5 and C6 acids, each independently selected from branched and/or linear alcohols, or C4 and C5 acids, each independently selected from branched and/or linear alcohols, or C6, C7, and C8 acids, each independently selected from branched and/or linear alcohols, or C5, C6, and C7 acids, each independently selected from branched and/or linear alcohols, and so on, to encompass every possible mixture of C4-C9 acids, preferably C6-C8 acids, each independently selected from branched and/or linear alcohols, in each case wherein said acids are preferably branched acids, are also useful to make these plasticizers.

In embodiments the branched acids moiety has an overall branching (i.e., an average branching), as measured by NMR techniques, less than 1.8 branches per molecule, more preferably less than 1.5 branches per molecule, and still more preferably less than 1.4 branches per molecule. In preferred embodiments, the lower limit on branching is 0.8 branches per chain, on average. The NMR technique used to measure branching is per se known in the art. See, for instance, WO 2006012989.

For PVC plastisols the esters of this invention, in particular the fast fusing plasticizers, give lower plastisol viscosity and improved processability versus those prepared with plasticizers from cyclohexanecarboxylic acid esters alone, particularly the di-isononyl cyclohexanediacid ester or the di-2-ethylhexyl cyclohexanediacid ester or the di-2-propylheptyl cyclohexanediacid ester

Plasticized polymer compositions according to embodiments of the invention offer advantages in other areas, such as in toy manufacturing, where the low viscosity and fusion properties would be an advantage over most alternatives, in automotive interior trim products because of their excellent UV stability, in extruded materials such as wire jacketing or tubing or hose or floor mats where the improved solvency and reduced fusion temperatures give high clarity products with low surface defects, in PVC film for uses such as wall paper or food containers or medical devices or stationary products, and in injection molded products for uses such as oxygen masks or cap liners or shoe soles. The fast fusing plasticiser according to the invention is especially beneficial as a non-yellowing viscosity modifier in vinyl sheet flooring manufacturing. In embodiments, the plasticizing system contributes to improved stain resistance. In a particularly preferred embodiment, the plasticizing system is useful as a process aid in the production of PVC toys through rotomolding and casting processes.

In an embodiment, the plasticizing system comprising at least one fast fusing plasticizer based on polyol esters of C4-C8 aliphatic acids, benzoic acids, or mixtures thereof may be mixed with plastics such as PVC in the amount of from 10 phr to 100 phr, where the descriptor phr refers to parts per hundred of resin or base polymer. Here, for example, 10 phr would refer to the weight of additive in pounds or kilos, in this case the plasticizer, added to 100 pounds or kilos of the PVC polymer.

In other embodiments, the plasticizing system of the invention may further comprise additives such as calcium carbonate fillers, Ca/Zn or Ba/Zn stabilizers, epoxidized soy bean oil, lubricants, pigments and dies or other colorants, antioxidants, and other stabilizers.

The PVC compositions of this invention can be processed into products through rotomolding, dipping, spraying, spreading, molding, extrusion, calendering, and injection molding, as well as by processing plastisols.

One widespread use of polyvinyl chloride is as a plastisol. A plastisol is a fluid or a paste consisting of a mixture of polyvinyl chloride and a plasticizer optionally containing various additives. A plastisol can be used to produce layers of polyvinyl chloride which are then fused to produce coherent articles of flexible polyvinyl chloride. Plastisols can be placed in cavity molds, then heated, to produced molded flexible PVC articles such as toys.

Plastisols can be used to make gloves by dipping molds into the plastisol, and then heating. Plastisols are useful in the production of flooring, tents, tarpaulins, coated fabrics such as automobile upholstery, in car underbody coatings, in moldings and other consumer products. Plastisols are also used in footwear, fabric coating, toys, flooring products and wallpaper. Plastisols typically contain about 40 to about 200 parts by weight, more typically 50 to 150 parts by weight, more typically 70 to 100 parts by weight of plasticizer.

Plastisols are usually made from polyvinyl chloride that has been produced by emulsion polymerization or micro suspension polymerization. The plastisol may be produced by the manufacturer of the polyvinyl chloride or by a compounder, and be shipped to the user in fluid form. Alternatively the plastisol may be produced by the user. In either instance, although particularly when the plastisol is produced by the manufacture of the polyvinyl chloride or a compounder, it is important that the plastisol viscosity be stable over time.

In a further embodiment, the present invention provides a process for the production of flexible polyvinyl chloride comprising forming a layer from a plastisol containing from 40 to 200 parts by weight preferably 50 to 150 parts by weight, more preferably 70 to 120 parts by weight of a plasticizer composition of the invention, per 100 parts by weight of polyvinyl chloride, and subsequently fusing the layer by the application of heat.

Recent studies have identified that C7 to C8 tri esters of glycerol perform as general purpose (GP) plasticizers, having a good balance of efficiency, volatility, cost, compatibility, stability, and low temperature flexibility. The solution temperature or the ability of these particular GP plasticizers to dissolve the PVC resin can be improved through the use of lower C5 to C6 acids. However as the molecular weight of the acid side chains is reduced, the volatility of the plasticizer increases and the utility of fast fusing plasticizers produced through this path diminishes. So it is desired to improve the solvation strength of the plasticizer while maintaining good volatility.

Several recent reporting, as discussed in the background section, have described plasticizers produced with various polyol esters and blends of 2-EH acid and benzoic acid. Our work suggests that esters of 2-EH acid have reduced compatibility with PVC, leading to exudation. Partial replacement of 2-EH acid with benzoic acid will improve the compatibility of the plasticizer. Companies such as Ferro and LG have in fact filed patent applications on similar 2-EH acid/benzoic acid plasticizers and LG has at least one commercially available plasticizer believe to be produced from mixtures of 2-EH acid and benzoic acid. It has been explained above, however, that the 2-EH acid component of the ester is less desirable for reasons of toxicity concern. One patent, U.S. Pat. No. 6,740,254, mentions plasticizer esters based on C4 and benzoic acids.

Examples of where these fast fusing plasticizers products can be used:

TABLE 1 Automotive underbody sealants PVC copolymer 100 Invention plasticizer 50 phr DINP 50 phr Calcium carbonate 100 phr  Other additives 20 phr

TABLE 2 Synthetic leather Top coat PVC 100 Invention plasticizer 15 phr  DINP 30 phr  Calcium carbonate 5 phr TXIB 3 phr Stabilizer 3 phr

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