Composition

Abstract

The present invention relates to a composition, in particular to a polyvinyl chloride-containing copolymer comprising: a. vinyl chloride and a second monomer, the second monomer being a monomer whose homopolymer has a glass transition temperature Tg below 82°C; and b. a composition comprising up to 10% by weight of a hydrotalcite compound, the hydrotalcite compound having up to 20.5% by weight of magnesium.

Description

[Technical field]

[0001] The present invention relates to compositions, particularly compositions comprising vinyl chloride-containing copolymers, that have good powder flow properties even after storage. [Background technology]

[0002] Polyvinyl chloride (PVC) is one of the most important thermoplastic materials on the market today. Due to its very good mechanical and physical properties, polyvinyl chloride is used in numerous applications. Several methods are known for the production of PVC. For example, PVC can be produced by suspension polymerization of vinyl chloride in the presence of a suspending agent in a suspension. This produces a slurry (or suspension) of PVC particles, typically with a particle size of around 100-200 μm. The resulting PVC slurry is then dried, usually by centrifugation followed by fluidized bed drying, resulting in porous (i.e., adsorptive) PVC. PVC produced by the suspension process is referred to as "S-PVC". S-PVC can absorb plasticizers to produce a dry mix. PVC can also be produced by a process commonly known as the paste or emulsion polymerization process. The emulsion polymerization process can be characterized by the production of a latex of polymer particles by polymerization, which are relatively small in particle size, typically 0.1-5 μm, relative to the S-PVC process. The latex is dried, for example by spray drying, to produce PVC particles in the form of agglomerates. The dried PVC polymer particles are typically much smaller than the dried particles produced by the suspension PVC process. It is known to add additives to PVC to make it suitable for different applications. It is also known to polymerize vinyl chloride monomer in the presence of a comonomer to improve properties. The most common comonomer for PVC is vinyl acetate.

[0003] PVC polymers are often manufactured and stored in the form of a dry powder. The powder can be stored and, if necessary, shipped in a "loose" form, for example stored in silos and shipped in tank trucks. PVC may also be stored (and shipped) in bags. During storage, the powder may agglomerate, which may result in the material having lumps or even becoming completely compacted. To prevent this, additives may be added to the powder. Such additives are generally known as "anti-caking agents" or "flow improvers". Compounds known in the art as anti-caking agents for PVC powders include calcium carbonate and silica (it should be noted that "flowability" in this sense refers to the flowability of the powder and not to properties such as "melt flow", which is a measure of the flowability or degree of flow of molten PVC).

[0004] PVC homopolymers themselves are generally quite rigid. It is known to add plasticizers to PVC to make it more flexible. These substances can be liquids or solids with low volatility. Overall, however, the flexibility of such products is not long-lasting. An alternative way to improve the flexibility of PVC is to "pre-plasticize" it by polymerizing the vinyl chloride monomer in the presence of a comonomer that improves the flexibility. Particularly preferred comonomers are acrylates and methacrylates. WO 2015 / 090657 describes a method for the preparation of polymers, for example, by reacting a vinyl halide with a second monomer, preferably an acrylate, and preparing the polymerization in a series of steps with controlled amounts of each monomer. The document states that if the ratio of monomers in the final product is correct, no additional plasticizer needs to be added. Summary of the Invention

[0005] The present inventors have now found that a particular class of hydrotalcites is useful as an anti-caking agent. In particular, hydrotalcites are known to be added to PVC to act as heat stabilizers and / or fillers. However, the present inventors have found that a particular class of hydrotalcites can be very effective anti-caking agents, even for significantly longer periods of time. This is particularly surprising, since "traditional" anti-caking agents and other hydrotalcite compounds have also been found to be ineffective for this purpose. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 shows the test results of Comparative Example 1. [Diagram 2] FIG. 2 shows the test results of Comparative Example 2. [Diagram 3] FIG. 3 shows the test results of Comparative Example 3. [Figure 4A-4B] FIG. 4A shows the test results of the sample of Comparative Example 4 before vibration was applied, and FIG. 4B shows the test results of the sample of Comparative Example 4 after the more vigorous vibration procedure. [Figure 5A-5B] FIG. 5A shows the test results of the sample of Comparative Example 5 before vibration was applied, and FIG. 5B shows the test results of the sample of Comparative Example 5 after the more vigorous vibration procedure. [Figure 6] FIG. 6 shows the test results of the sample of Example 1 before vibration was applied. [Figure 7] FIG. 7 shows the test results of the sample of Example 2 before vibration was applied. [Figure 8] FIG. 8 shows the test results of the sample of Example 3 before vibration was applied. [Figure 9] FIG. 9 shows the test results of the sample of Example 4 before vibration was applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Thus, a first aspect of the present invention provides a method for producing a method for treating a pulmonary circulation comprising the steps of: a. a polyvinyl chloride-containing copolymer comprising vinyl chloride and a second monomer, the second monomer being a monomer whose homopolymer has a glass transition temperature Tg lower than 82° C.; and b. up to 10% by weight of hydrotalcite compound wherein the hydrotalcite compound has no more than 20.5% by weight magnesium. As a first component, the composition comprises a polyvinyl chloride-containing copolymer. The copolymer comprises vinyl chloride and a second monomer. The second monomer is a monomer whose homopolymer has a glass transition temperature Tg lower than 82°C. Such monomers are known in the art, and in fact are commonly referred to as "soft monomers". Thus, examples of monomers that are particularly preferred for the second monomer in the copolymer component of the present invention include vinyl carboxylates, vinyl ethers, olefins, and alkyl (meth)acrylates. Particularly preferred second monomers are vinyl carboxylates, especially vinyl acetate, and alkyl (meth)acrylates. In a preferred embodiment, the second monomer is a monomer whose homopolymer has a glass transition temperature Tg below 70° C., for example below 50° C. Preferred second monomers may be monomers whose homopolymer has a glass transition temperature below 20° C., or even below 0° C. The glass transition temperature of poly(vinyl acetate) is, for example, 30° C., while poly(alkyl acrylates) with C1-C10 alkyl groups generally have a glass transition temperature below 0° C. The glass transition temperature of poly(butyl acrylate) is, for example, −53° C.

[0008] The glass transition temperature of a polymer is a well-known parameter that can be found in textbooks and data tables, and can also be measured experimentally. In the present invention, the glass transition temperature Tg is the value obtained by Dynamic Mechanical Analysis under the conditions set out in ASTM E1640-18 "Standard Test Method for Assignment of the Glass Transition Temperature by Dynamic Mechanical Analysis". The copolymers can be made by any suitable copolymerization method in which vinyl chloride monomer is copolymerized with a second monomer, including suspension and emulsion polymerization methods, which are well known in the art. The copolymer typically comprises at least 40% by weight vinyl chloride and up to 60% by weight of the second monomer, however it is preferred that the copolymer comprises at least 50% by weight vinyl chloride, for example at least 60% by weight vinyl chloride.

[0009] In addition to vinyl chloride and the second monomer, other monomers may also be present. In particular, and for the avoidance of doubt, the term "copolymer" as used herein encompasses polymers containing two or more monomers. It includes polymers with only two types of monomers, namely vinyl chloride and the second monomer, and also polymers containing three or more monomers, namely vinyl chloride, the second monomer, and one or more other monomers (polymers containing three monomers may also be referred to as terpolymers, and as such are included within the definition of copolymer herein). Any other monomers present (i.e., in addition to vinyl chloride and the second monomer) may also be monomers whose homopolymers have a glass transition temperature Tg lower than 82°C, and in some preferred embodiments may meet the preferred characteristics of the second monomer. However, they may also be monomers whose homopolymers have a glass transition temperature Tg of 82°C or higher, in some embodiments. In all cases where there is more than one monomer other than vinyl chloride (hereafter more than one "comonomer"), the second monomer is preferably present as at least 50 mol % of the total comonomers present (in this case, for example, if there are more than one comonomer and both qualify as a second monomer, the one present in the greatest amount will be the second monomer for purposes of the claims).

[0010] In a preferred embodiment, the second monomer is an alkyl (meth)acrylate. In this embodiment, the copolymer typically comprises at least 40% by weight of vinyl chloride and up to 60% by weight of alkyl (meth)acrylate. However, it is preferred that the copolymer comprises at least 50% by weight of vinyl chloride, for example at least 60% by weight of vinyl chloride. In addition to vinyl chloride and alkyl (meth)acrylate, other comonomers may also be present, including one or more other second monomers as previously defined. The copolymer most preferably comprises at least 70% by weight vinyl chloride and at most 30% by weight alkyl (meth)acrylate. Particularly preferred polyvinyl chloride-alkyl (meth)acrylate copolymers for the first component of the present invention may comprise at least 90% by weight vinyl chloride and at most 10% by weight alkyl (meth)acrylate. The term "alkyl (meth)acrylate" is used herein as a shorthand to refer to alkyl acrylates and alkyl methacrylates. For example, butyl (meth)acrylate refers to butyl methacrylate and butyl acrylate. In a preferred embodiment, the copolymer is a polyvinyl chloride-alkyl acrylate copolymer, however, as described below, even when only acrylate copolymers are referred to, the reference applies equally to copolymers formed with other second monomers, including equivalent methacrylate copolymers, unless the context clearly dictates otherwise.

[0011] The alkyl (meth)acrylate preferably comprises a C1-C10 alkyl group. Preferred alkyl groups comprise a C2-C6 alkyl group. As already mentioned, the preferred alkyl (meth)acrylate in the copolymer component of the composition of the present invention is an alkyl acrylate rather than an alkyl methacrylate. Particularly preferred alkyl (meth)acrylates are ethylhexyl acrylate and n-butyl acrylate, with n-butyl acrylate being most preferred. As a second component, the composition comprises up to 10% by weight of a hydrotalcite compound, the hydrotalcite compound having up to 20.5% by weight of magnesium. Hydrotalcites are generally layered double hydroxides containing magnesium, aluminum, carbonate anions and hydroxide anions. Unmodified hydrotalcites have the general formula Mg6Al2CO3(OH) 16 4H2O. This material has a magnesium content of 24.14% by mass. However, hydrotalcite has the formula Mg6Al2CO3(OH) 16Hydrotalcites having different compositions compared to that given by 4H2O are known. For example, hydrotalcites may be partially substituted with different metals or different anions. Such hydrotalcites are generally considered to be "modified hydrotalcites", the term "modified hydrotalcites" being a layered double hydroxide containing magnesium, aluminum, carbonate anions and hydroxide anions, but with the formula Mg6Al2CO3(OH) 16 · Refers to hydrotalcites that have a formula different from 4H2O.

[0012] Therefore, the hydrotalcite used in the present invention is a modified hydrotalcite in general terms, and in more specific terms is a modified hydrotalcite having a reduced magnesium content of 20.5 mass % or less. Thus, when applied to the hydrotalcites having a magnesium content of 20.5% by weight or less used in the present invention, the terms "hydrotalcite" and "modified hydrotalcite" are synonymous. The hydrotalcite of the present invention has a significantly reduced magnesium content compared to unmodified hydrotalcite. The reduced magnesium content in the hydrotalcite of the present invention is typically achieved by removing or replacing magnesium in the structure during synthesis or by post-synthesis treatment of the structure. This can be achieved by any suitable method known in the art. Several modified hydrotalcite compounds are commercially available. The inventors have found that hydrotalcites modified to significantly reduce the magnesium content are particularly effective as anti-caking agents for polyvinyl chloride-alkyl (meth)acrylate copolymers. In contrast, similar materials, except that they have a higher magnesium content, are not as effective. This is shown in the examples provided below.

[0013] In a preferred composition of the present invention, the hydrotalcite compound has 20% by weight or less of magnesium. Typically, the hydrotalcite compound has at least 10% by weight of magnesium. In some embodiments, the hydrotalcite may contain at least 18% by weight of magnesium, for example, 18% to 20% by weight of magnesium. In other embodiments, the hydrotalcite may contain 18% by weight of magnesium, for example, 16% by weight or less of magnesium, for example, 14% to 16% by weight of magnesium. In a further preferred composition, the hydrotalcite compound contains at least one metal selected from Sn, Pb, Ca, Ba, Zn and Cd, and preferably contains at least 0.2% by mass of at least one metal selected from Sn, Pb, Ca, Ba, Zn and Cd. More preferably, the hydrotalcite compound contains at least 1% by mass of at least one metal selected from Sn, Pb, Ca, Ba, Zn and Cd. In particularly preferred embodiments, the at least one metal is Zn or Ca, and most preferably, the at least one metal is Zn.

[0014] When zinc is present, preferred compositions are those in which the hydrotalcite compound contains at least 10% by weight of zinc, as such compounds have shown particularly good effectiveness as anti-caking agents, even after long-term storage of compositions containing them. In a further embodiment which may be combined with the already mentioned preferences, it is preferred that the hydrotalcite compound contains less than 150 ppm (by weight) of sulfur, preferably less than 100 ppm (by weight) of sulfur. Due to the reduced magnesium content, the hydrotalcite compound in the composition of the present invention tends to have a lower Mg / Al ratio than unmodified hydrotalcite. In a preferred embodiment, the hydrotalcite compound has a Mg / Al molar ratio of 2.2 or less, for example 2.0 or less. The Mg / Al ratio may be, for example, 1.50 to 2.00, for example 1.50 to 1.90. The composition of the present invention can be formed in any suitable manner by combining the polyvinyl chloride-containing copolymer with the hydrotalcite compound. In a particularly preferred manner, the hydrotalcite is introduced into the polyvinyl chloride-containing copolymer after the copolymer is produced in the polymerization reactor, but before it is completely dried. In particular, it is known that the polyvinyl chloride-containing copolymer may begin to agglomerate during drying, and to alleviate this, a "traditional" anti-caking agent is added before drying. The hydrotalcite compound of the present invention can then act as an effective anti-caking agent during drying (i.e., instead of the more conventional anti-caking agent), and also provide the longer-term anti-caking effect found.

[0015] In contrast, "traditional" anti-caking agents have been found to be effective during drying but not over significantly longer periods, such as during storage. Thus, in a second aspect, there is provided a use of hydrotalcite for reducing caking of a composition comprising a polyvinyl chloride-containing copolymer comprising vinyl chloride and a second monomer, the second monomer being a monomer whose homopolymer has a glass transition temperature Tg below 82°C, and the hydrotalcite compound having 20.5% by weight or less of magnesium. The copolymer and the hydrotalcite of this second aspect are preferably those defined in the first aspect. EXAMPLES

[0016] Experimental procedure 1) Preparation of polyvinyl chloride-containing copolymers In a polymerization reactor of 94 L volume and equipped with stirrer, 54 Kg of water, 3197 gr of polyvinyl alcohol solution in water with a degree of hydrolysis of 72.5% and of 25.75 gr / Kg, 682 gr of polyvinyl alcohol solution in water with a degree of hydrolysis of 88% and of 30.15 gr / Kg, 30 gr of antifoaming agent, 30 gr of buffer solution (Sodium Hexametaphosphate - NaHP) with a degree of hydrolysis of 30 gr / Kg in water, 50 gr of heat stabilizer (Calcium Stearate) with a dispersion of 500 gr / Kg in water, and 5 gr of chain transfer agent (1-dodecanethiol). Once the reactor was closed, the agitation speed was set to 70 rpm and two cycles of vacuum were applied followed by a nitrogen purge and a final vacuum was applied. Then 4470 gr butyl acrylate was charged followed by 5215 gr vinyl chloride and the agitation speed was set to 300 rpm. The polymerization temperature was raised to 70°C using a double jacket. At the polymerization temperature (70°C) an introduction of 9.0 g of a solution of diethyl peroxydicarbonate in dioctyl adipate with a concentration of 300 gr / Kg is introduced to start the polymerization. A second introduction of 13 gr of a solution of diethyl peroxydicarbonate in dioctyl adipate with a concentration of 300 gr / Kg at CR>5% and a third introduction of 15 gr of a solution of diethyl peroxydicarbonate in dioctyl adipate with a concentration of 300 gr / Kg at CR>10% is introduced. The reaction was kept under these conditions until the conversion of butyl acrylate reached a value higher than 80%. Then 30 gr of a solution of inhibitor (KI) at 10 gr / Kg in water is added and the polymerization temperature is cooled to below 45°C. Then 5948 gr of vinyl chloride were charged, followed by 434 gr of a solution of polyvinyl alcohol in water at 31.65 gr / Kg and a degree of hydrolysis of 80%, and finally 30 gr of a solution of diethyl peroxydicarbonate in dioctyl adipate at a concentration of 300 gr / Kg. The reaction was kept under these conditions until the total conversion of vinyl chloride reached 63.7%. Then 30 gr of a solution of an inhibitor (caustic soda - NaOH) at 220 gr / Kg in water and 30 gr of an antifoaming agent were added to the polymerization medium. The unreacted vinyl chloride was removed by depressurizing the reactor. The suspension was then separated by filtration.

[0017] The first portion was separated and dried in a fluid bed dryer at 60° C. with air to obtain a polyvinyl chloride-containing copolymer product. The volatiles before drying were about 11% by weight. After drying, the volatiles were less than 0.3% by weight and the residual butyl acrylate monomer was 12 ppm. 1 The butyl acrylate content in the copolymer determined by H NMR was 38.6% by weight, the bulk density was 0.567 g / cm3, and the average particle size was 236 μm. Further portions were dried similarly, except that in each case 4 phr (parts per million) of anti-caking agent was added prior to drying, details of the anti-caking agents are given below. In all cases, the addition of anti-caking agents resulted in free-flowing powder samples after the drying step.

[0018] 2) Consolidation procedure and fluidity evaluation The samples prepared above were each subjected to the following procedures. Approximately 20 g of sample was placed into a cylindrical mould of 3 cm diameter and placed in a compressive strength tester manufactured by Industrial Concept and Assistance, Bierges, Belgium. The sample was then compressed axially in the mold with a force that increased stepwise from 10 kg (98.1 N) to 100 kg (981 N). This compaction is designed to mimic in the short term the long term compaction that can occur during storage of PVC powder. At the end of the test, the mold containing the compressed sample is positioned 19 cm above a stainless steel grid at the base of the beaker with a square opening measuring 1.8 cm on a side.

[0019] In the first step, the sample is pushed out of the mold and dropped onto the grid. The beaker is then gently tapped twice. The sample is considered to have "excellent" flow if it passes completely through the grid at this step, either before or after the gentle tapping, without any compaction. If the sample is fully or partially consolidated and some powder remains on the grid after the first step, gently shake the beaker 5-10 times and re-evaluate the sample. If the sample then flows completely through the grid, it is considered to have good flowability. If the sample is still completely or partially comparable, the sample is shaken further, especially more vigorously, 15-20 times. If the sample now flows completely through the grid, it is considered to have flowability but "low" flowability. If some, but not all, remains on the grid, the flowability is considered to be very low, and if all or most of the original sample remains as a consolidated column, the sample is considered to have no flowability ("none").

[0020] To summarize: [Table 1]

[0021] Comparative Example 1 In this comparative example, the sample had no anti-caking agent added. The results of the test are shown in Figure 1. The sample is completely consolidated and has no flowability according to the criteria stated above.

[0022] Comparative Example 2 In this example, 4 phr of D-mannitol was added to the samples before drying. D-mannitol was supplied by Sigma-Aldrich and is a known anti-caking agent used in the food industry. The results of the test are shown in Figure 2. The sample was fully consolidated and is considered non-flowable by the criteria stated above. Comparative Example 3 In this example, 4 phr of hydrotalcite ("Hydrotalcite 1") was added to the sample before drying. Hydrotalcite 1 is a commercially available hydrotalcite with a Mg content of 22.8 wt%. The results of the test are shown in Figure 3. The majority of the samples are still consolidated and are considered non-flowable by the criteria stated above. Comparative Example 4 In this example, 4 phr of a different hydrotalcite ("Hydrotalcite 2") was added to the sample before drying. Hydrotalcite 2 is a commercially available hydrotalcite with a Mg content of 20.8 wt. %. The results of the test are shown in Figures 4A and 4B, where Figure 4A shows the sample before vibration and Figure 4B shows the sample after a more vigorous vibration procedure. The sample is considered to have "low" flowability by the criteria set forth above.

[0023] Comparative Example 5 In this example, 4 phr of a different hydrotalcite ("Hydrotalcite 3") was added to the sample before drying. Hydrotalcite 3 is a commercially available hydrotalcite with a Mg content of 22.3 wt%. The results of the test are shown in Figures 5A and 5B, where Figure 5A shows the sample before vibration and Figure 5B shows the sample after a more vigorous vibration procedure. The sample is considered to have "low" flowability by the criteria set forth above.

[0024] Example 1 In this example, 4 phr of a different hydrotalcite ("Hydrotalcite 4") was added to the sample before drying. Hydrotalcite 4 is a commercially available hydrotalcite with a Mg content of 20.0 wt. %. The results of the test are shown in Figure 6, which shows the sample before vibration was applied and shows that the sample passed completely through the grid. The sample is considered to have excellent flowability by the criteria stated above.

[0025] Example 2 In this example, 4 phr of a different hydrotalcite ("Hydrotalcite 5") was added to the sample before drying. Hydrotalcite 5 is a commercially available hydrotalcite with a Mg content of 15.1 wt. %. The results of the test are shown in Figure 7, which shows the sample before vibration was applied and shows that the sample passed completely through the grid. The sample is considered to have excellent flowability by the criteria stated above. Example 3 In this example, 4 phr of a different hydrotalcite ("Hydrotalcite 6") was added to the sample before drying. Hydrotalcite 6 is a commercially available hydrotalcite with a Mg content of 19.9 wt. %. The results of the test are shown in Figure 8, which shows the sample before vibration was applied and shows that the sample passed completely through the grid. The sample is considered to have excellent flowability by the criteria stated above.

[0026] Example 4 In this example, 4 phr of a different hydrotalcite ("Hydrotalcite 7") was added to the sample before drying. Hydrotalcite 7 is a commercially available hydrotalcite with a Mg content of 14.3 wt. %. The results of the test are shown in Figure 9, which shows the sample before vibration was applied and shows that the sample passed completely through the grid. The sample is considered to have excellent flowability by the criteria stated above.

[0027] The results are summarized in Table 2, along with details of some other properties of the additive. [Table 2]

[0028] Comparative Example 1 shows that the PVC copolymer is highly compacted after compression. D-mannitol is a traditional additive, but does not result in a flowable product after compaction testing. Hydrotalcites 1, 2 and 3 are hydrotalcite materials each having greater than 20.5 wt. % magnesium and the flowability of the resulting materials is "poor" at best. Examples 1 to 4, in contrast, show that hydrotalcite materials having less than 20.5 wt. % magnesium in each case result in excellent flowability of the product even after compaction testing.

Claims

1. a. a polyvinyl chloride-containing copolymer comprising vinyl chloride and a second monomer, the second monomer being a monomer whose homopolymer has a glass transition temperature, Tg, lower than 82°C; and b. up to 10% by weight of a hydrotalcite compound Contains the second monomer is selected from vinyl acetate and alkyl (meth)acrylate; 1. A composition wherein the hydrotalcite compound has no more than 20.5% by weight of magnesium.

2. The composition of claim 1 wherein the second monomer is an alkyl (meth)acrylate.

3. The composition of claim 1, wherein the second monomer is vinyl acetate.

4. a. a polyvinyl chloride-containing copolymer comprising vinyl chloride and an alkyl (meth)acrylate, and b. up to 10% by weight of a hydrotalcite compound wherein the hydrotalcite compound has 20.5 wt. % or less of magnesium.

5. The composition of claim 2 or 4, wherein the alkyl (meth)acrylate comprises a C2-C8 alkyl group.

6. The composition of claim 5, wherein the alkyl (meth)acrylate is ethylhexyl acrylate or n-butyl acrylate.

7. The composition of any one of claims 1 to 4, wherein the polyvinyl chloride-containing copolymer is a polyvinyl chloride-butyl acrylate copolymer.

8. A composition according to any one of claims 1 to 4, wherein the copolymer comprises at least 60% by weight of vinyl chloride, preferably at least 70% by weight of vinyl chloride.

9. A composition according to any one of claims 1 to 4, wherein the hydrotalcite compound has up to 20% by weight of magnesium, for example 14% to 20% by weight of magnesium.

10. 5. The composition according to claim 1, wherein the hydrotalcite compound comprises at least 0.2% by weight, preferably at least 1% by weight, of at least one metal selected from Sn, Pb, Ca, Ba, Zn and Cd.

11. 11. The composition of claim 10, wherein the at least one metal is Zn or Ca, preferably the at least one metal is Zn.

12. The composition according to any one of claims 1 to 4, wherein the hydrotalcite compound contains at least 10% by weight of zinc.

13. 5. The composition according to any one of claims 1 to 4, wherein the hydrotalcite compound has a molar ratio of Mg / Al of not more than 2.2, preferably the hydrotalcite compound has a molar ratio of Mg / Al of 1.50 to 2.

00.

14. 1. Use of hydrotalcite to reduce caking of a composition comprising a polyvinyl chloride-containing copolymer comprising vinyl chloride and a second monomer, wherein the second monomer is a monomer whose homopolymer has a glass transition temperature Tg lower than 82°C, the second monomer is selected from vinyl acetate and alkyl (meth)acrylate, and the hydrotalcite compound has 20.5% by weight or less of magnesium.

15. Use according to claim 14, wherein the polyvinyl chloride-containing copolymer and / or the hydrotalcite is as defined in any one of claims 1 to 4.

Images