High molecular weight acrylic processing aid concentrate for thermoplastic processing

Abstract

Disclosed is a pelletized composition comprising a high molecular weight processing aid and optionally one or more additional components. The high molecular weight processing aid is present in an amount ranging from 50% to 100% by weight relative to the total weight of the composition, and the one or more additional components are present in an amount ranging from 0% to 50% by weight relative to the total weight of the composition. The pelletized composition does not comprise a carrier resin. The pelletized composition is in the form of particles having a D50 particle size ranging from 1 to 30 mm and a D10 particle size of at least 50% of the D50 particle size.

Description

HIGH MOLECULAR WEIGHT ACRYLIC PROCESSING AID CONCENTRATEFOR THERMOPLASTIC PROCESSINGFIELD OF THE INVENTIONL0001 J The field of this invention is high molecular weight acrylic processing aid concentrates.BACKGROUND

[0002] Polyvinyl chloride (PVC) is widely used on a variety of applications, including building and constructions products, such as fencing, siding, decking, trim boards, fascia boards, window frames, sills, and doors. PVC polymer virgin resin is generally supplied in powder form. The PVC is typically formulated by dry blending with other components, which are also in powder form, and thermally processed by melt extrusion into the finished product.

[0003] Acrylic processing aids are commonly one of the powdered components incorporated into the PVC formulation. Acrylic processing aids are typically added in parts per hundred resin (phr) to the PVC.

[0004] Environmental sustainability is driving interest in reusing and recycling materials, including PVC, to increase the amount of post-consumer or post-industrial waste in the material stream. When incorporated into PVC formulations, post-consumer or postindustrial scrap PVC is typically mixed with virgin PVC powder. However, problems arise with the use of scrap PVC.

[0005] Recycled PVC is pulverized from already formed parts. The pulverized PVC particles are typically much larger than the virgin PVC powder. The difference in particle size presents problems when mixing prior to extrusion. These problems may include particle separation and non-uniform mixing of the composition.

[0006] Similarly, when pulverized PVC particles, which typically have a particle size of greater than 35 mesh (500 microns), more commonly greater than 18 mesh (1 mm), are mixed with commercially available powdered processing aids, which have an average particle size of about 50 to 500 microns, issues arise due to the different sizes of the pulverized PVC and processing aid. Similar to the mixing of pulverized PVC with virgin PVC powder, the mixing of pulverized PVC with powdered processing aids leads to particle segregation, which in turn results in non-uniform mixing prior to extrusion.

[0007] Another problem when using scrap PVC arises due to the fact that many PVC formulations already contain added components from the original formulation. Because these added components are not removed during the pulverization process, the scrap PVC particles will have a different composition than the virgin PVC powder.

[0008] WO 2022 / 072220 Al discloses a composition comprising a high molecular weight processing aid wherein the composition has an average particle size of at least 2 mm. The composition disclosed by WO 2022 / 072220 Al, however, requires the presence of a carrier resin, as either a passive or active component of the composition.

[0009] The presence of a carrier may lead to problems using scrap PVC due to variations in the composition. When using scrap PVC, it is desirable to have greater control over the composition when adding processing aids or other components.

[0010] The present invention seeks to solve one or more of the problems identified above.SUMMARY OF THE INVENTION

[0011] Disclosed herein is a pelletized composition comprising a high molecular weight processing aid and one or more additional components selected from the group consisting of lubricants, heat stabilizers, antioxidants, fillers, and coloring agents. The high molecular weight processing aid is present in an amount ranging from 50 to 100 wt% relative to the total weight of the composition and the one or more additional components are present in an amount ranging from 0 to 50 wt% relative to the total weight of the composition. The composition does not comprise a carrier resin. The pelletized composition is in the form of particles having a D50 particle size ranging from 1 to 30 mm and a dlO particle size of at least 50% of the D50 particle size.

[0012] Also disclosed herein is a polyvinyl chloride composition comprising a polyvinyl chloride resin and a pelletized composition comprising a high molecular weight processing aid and one or more additional components selected from the group consisting of lubricants, heat stabilizers, antioxidants, fillers, and coloring agents, wherein the high molecular weight processing aid is present in an amount ranging from 50 to 100 wt% relative to the total weight of the composition, and the one or more additional components are present in an amount ranging from 0 to 50 wt% relative to the total weight of the composition. The pelletized composition does not comprise a carrier resin. The pelletized composition is in theform of particles having a D50 particle size ranging from 1 to 30 mm and a dlO particle size of at least 50% of the D50 particle size .

[0013] A method of preparing the polyvinyl chloride composition and an article made therefrom are also disclosed.DETAILED DESCRIPTION OF THE INVENTION

[0014] Disclosed herein is an improved processing aid for use in polyvinyl chloride compositions. The processing aid of the present invention is a pelletized composition comprising a high molecular weight processing aid and one or more additional components, wherein the pelletized composition is in the form of particles having a D50 particle size ranging from 1 to 30 mm and a dlO particle size of at least 50% of the D50 particle size . The pelletized composition does not comprise a carrier resin.

[0015] As used herein, “pelletized composition” is a composition comprising particles in the form of aggregated, clustered, grouped, coalesced, consolidated, or conglomerated smaller particles. For example, a pelletized composition may be formed by first drying a composition to form a powder, followed by further processing the powder to form larger collections of the powdered particles.

[0016] As used herein, “high molecular weight processing aid” is a processing aid having a weight average molecular weight of at least 500,000 g / mol. Preferably, the high molecular weight processing aid has a weight average molecular weight of at least 5,000,000 g / mol. More preferably, the high molecular weight processing aid has a weight average molecular weight of at least 10,000,000 g / mol.

[0017] As used herein, “average particle size” is the arithmetic mean of all possible diameters. The aspect ratio of the particles is the ratio of the longest to the shortest diameters. The particles may have any shape, including for example, spherical, cylindrical, oblong, cuboid, prismatic, or irregular. As used herein, the terms “DIO” and “D50” particle size values refer to the size at which 10% and 50%, respectively, of mass of the pelletized composition is accounted for by having a diameter less than or equal to the specified value. Thus, the DIO value is the particle size at which 10 wt% of all particles of the pelletized composition are smaller than the indicated particle size. The D50 value is the “weight median particle size” at which 50 wt% of all particles of the pelletized composition are smaller than the indicated particle size.

[0018] Suitable high molecular weight polymer processing aids useful in the present invention include polymers and copolymers containing vinyl aromatic, (meth)acrylonitrile, and alkyl (meth) acrylate monomers. As used herein, “(meth)acrylonitrile” includes both methacrylonitrile and acrylonitrile monomers. Similarly, “alkyl (meth)acrylate” includes both alkyl methacrylate and alkyl acrylate monomers.

[0019] Preferably, the high molecular weight processing aid is a copolymer comprising alkyl (meth)acrylate monomers. For example, the high molecular weight processing aid is a copolymer comprising methyl (meth)acrylate. The methyl (meth)acrylate copolymer may comprise, for example, monomers selected from other alkyl (meth) acrylate monomers, such as ethyl acrylate, butyl acrylate, and 2-ethyl hexyl acrylate. An exemplary high molecular weight processing aid comprises copolymers containing a majority (i.e., at least 50% by weight relative to the total weight of the high molecular weight processing aid) of methyl methacrylate (“MMA”) and a minority (i.e., less than 50% by weight relative to the total weight of the high molecular weight processing aid) of alkyl acrylates, such as ethyl acrylate, butyl acrylate, or 2-ethyl hexyl acrylate.100020] The high molecular weight processing aid may comprise core-shell-type processing aids that combine an external lubricant functionality with that of processing aid functionality. These “lubricating-processing aids” provide the typical processing-performance properties of acrylic processing aids, but have the added advantage of an external-lubricant function, which improves flow and machine running time by significantly reducing sticking of the molten polyvinyl chloride resin to hot metal surfaces of the processing equipment.

[0021] Commercially available high molecular weight processing aids are available from The Dow Chemical Company, Midland, Michigan, under the tradenames PARALOID™ and SURECEL™. One preferred high molecular weight processing aid is SURECEL™ 21607-XP,

[0022] The high molecular weight processing aid is preferably present in an amount ranging from 50% to 100 wt% relative to the total weight of the pelletized composition. For example, the high molecular weight processing aid can be present in an amount of at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, or at least 95% by weight relative to the total weight of the pelletized composition. The high molecular weight processing aid can be present in an amount less than 95%, less than 90%, less than 85%, less than 80%, less than 70%, or less than 60% by weight relative to the total weight of the pelletized composition. Preferably, the high molecular weight processing aid ispresent in an amount ranging from 60 to 100 wt%, more preferably from 70 to 100 wt%, even more preferably from 80 to 100 wt%, and still more preferably from 90 to 100 wt% relative to the total weight of the pelletized composition. In a preferred embodiment, the high molecular weight processing aid comprises 100 wt% of the total weight of the pelletized composition, i.e., the pelletized composition consists of the high molecular weight processing aid.

[0023] The composition may further comprise one or more additional components, including lubricants, heat stabilizers, antioxidants, fillers, coloring agents, and other additives. When present, these additional components may be present in an amount ranging from greater than 0% to 50% by weight relative to the total weight of the pelletized composition, such as, for example, from greater than 0% to 40%, from 1% to 35%, from 2% to 30%, or from 5% to 25% by weight relative to the total weight of the pelletized composition.

[0024] Suitable lubricants that may be used in the composition include internal and external lubricants, as well as lubricants that have a balance between internal and external lubricating properties. Generally, external lubricants determine the behavior of hot plastic compounds at interfaces with other materials such as delaying fusion / gelation and reducing sticking and friction, and internal lubricants influence rheological processes inside the polymer phase such as providing lubrication between the polymer chains and improving melt flow. Examples of lubricants include, for example, esters such as monoglycerin esters, hydrocarbon waxes such as paraffin wax, polyethylene wax, and oxidized polyethylene wax, esters, stearyl alcohol, fatty acids such as stearic acid, fatty-acid amides such as ethylene bisstearamide (i.e., two C16-C18 alkyl groups covalently bonded to a central polar amide group), soaps, and stearate salts such as calcium stearate. Suitable external lubricants include, but are not limited to, long chain montan acid (i.e., a long chain C28-C32 alkyl group covalently bonded to a polar group, such as carboxylic acid), paraffins and hydrocarbons having short branched chain alkyl groups, n-paraffins having long straight chain hydrocarbons, polyethylene waxes having very long straight hydrocarbon chains with a few branches. Suitable lubricants that provide a balance between internal and external lubrication include synthetic fatty acid partially saponified with calcium and long-chain montan ester types (e.g., Wax OP, and Wax E available from American Hoechst Corp., Mountainside, N.J.). Further information on lubricants for PVC can be found in a review byMcMurrer, M. C., Ed. “Update: Lubricants for PVC”, Plastics Compounding, pp. 74.-90 July / August 1982.

[0025] Suitable antioxidants include, but are not limited to, phenolic antioxidants, phosphate antioxidants, sulfur antioxidants, and blends thereof. Exemplary antioxidants include those sold by Adeka under the ADK STAB brand.

[0026] Examples of suitable heat stabilizers for the composition include, but are not limited to organotin stabilizers (e.g., MARK® organotin heat stabilizers from Galata Chemicals), mixed metal heat stabilizers (e.g., MARK® liquid and solid mixed metal heat stabilizers from Galata Chemicals), and phosphite stabilizers (e.g., MARKPHOS® phosphite heat stabilizers from Galata Chemicals).

[0027] The pelletized compositions of the present invention do not comprise a carrier resin. This includes both passive carrier resins, as well as active carrier resins which may have some activity as a processing aid. Therefore, the pelletized compositions of the present invention do not comprise carrier resins, such as, immiscible polymers such as polyethylene, polyethylene terephthalate, polypropylene, and inorganic materials such as talc, calcium carbonate, and fibers, or active carrier resins, such as, terpolymers such as ethylene terpolymers and polyethylene waxes.

[0028] In WO 2022 / 072220 Al, a composition is disclosed comprising a high molecular weight processing aid and a carrier resin. The present inventors have surprisingly discovered that a pelletized composition can be prepared without the presence of a carrier resin.

[0029] The pelletized composition of the present invention may be prepared, for example, by blending the high molecular weight processing aid and the one or more additional components, if present, as a powder and then processing the blended composition to form larger particles. The present inventors have found that special processing is required to form the larger particles to avoid decreasing the molecular weight of the processing aid, which can occur in processes that impart shear forces during processing. For example, the particles of the pelletized composition can be formed by compaction, compression, or through low-shear extrusion.

[0030] The composition of the present invention is present in the form of particles having a D50 particle size of at least No. 18 mesh or 1 mm. For example, the particles may have an average particle size of at least No. 10 mesh (2 mm), at least No. 8 mesh (2.38 mm), at least No. 6 mesh (3.36 mm), or at least No. 5 mesh (4 mm). When used with a finelypulverized resin, the average particle size of the composition may be smaller than No. 10 mesh. Preferably, the D50 particle size of the particles of the pelletized composition ranges from 1 mm to 30 mm, more preferably from 2 mm to 20 mm.

[0031] The D10 particle size of the particles of the pelletized composition are at least 50% of the D50 particle size. For example, if the D50 particle size is 2 mm, the D10 particle size is at least 1 mm. Preferably, the D10 particle size is at least 60% of the D50 particle size, more preferably at least 70% of the D50 particle size, and even more preferably at least 80% of the D50 particle size. When the D10 particle size is closer to the D50 particle size, it is believed that fewer small particles are present in the pelletized composition that would increase the possibility of stratification or segregation of the composition in which the pelletized composition is used.

[0032] The pelletized composition may comprise, consist of, or consist essentially of 50 to 100 wt% of the high molecular weight processing aid and 0 to 50 wt% of the one or more additional components selected from the group consisting of lubricants, heat stabilizers, antioxidants, fillers, and coloring agents, wherein the weight percentages are based on the total weight of the composition. As used herein, the term “consist essentially of’ means that the pelletized composition comprises less than 5 wt% of any component other than the high molecular weight processing aid and the one or more additional components selected from the group consisting of lubricants, heat stabilizers, antioxidants, fillers, and coloring agents. Preferably, the pelletized composition comprises less than 2 wt% of any component other than the high molecular weight processing aid and the one or more additional components selected from the group consisting of lubricants, heat stabilizers, antioxidants, fillers, and coloring agents.

[0033] A polyvinyl chloride (PVC) composition can be prepared by blending a polyvinyl chloride resin with the particles of the pelletized composition comprising the high molecular weight processing aid. The pelletized composition comprising the high molecular weight processing aid may be present in the PVC composition in an amount ranging from, for example, 0.5 to 20 parts per hundred resin (phr). For example, the pelletized composition comprising the high molecular weight processing aid may be present in the PVC composition in an amount ranging from, for example, 1 to 15 phr or from 2 to 10 phr.

[0034] Preferably, the polyvinyl chloride resin comprises recycled PVC. As used herein, “recycled PVC” refers to post-consumer or post-industrial scrap, i.e., non-virgin PVC. Typically, recycled PVC is processed by pulverizing articles made of polyvinyl chloride.The pulverization process produces particles of polyvinyl chloride having an average particle size ranging from, for example, 1 mm to 30 mm. Preferably, the recycled PVC has an average particle size 0.5 to 15 times the average particle size of the pelletized composition, more preferably, from 1 to 10 times the average particle size of the pelletized composition, and even more preferably from 1 to 5 times the average particle size of the pelletized composition. Preferably, the particles of the pelletized composition comprising the high molecular weight processing aid have an average size that is at least 10% of the average size of the polyvinyl chloride resin particles. For example, when the average particle size of the polyvinyl chloride resin is 20 mm, the average particle size of the particles comprising the high molecular weight processing aid is at least 2 mm. More preferably, the particles of the composition comprising the high molecular weight processing aid have an average size that is at least 20% of the average size of the polyvinyl chloride resin particles. Even more preferably, the particles of the composition comprising the high molecular weight processing aid have an average size that is at least 30% of the average size of the polyvinyl chloride resin particles, and still more preferably, the particles of the composition comprising the high molecular weight processing aid have an average size that is at least 40% of the average size of the polyvinyl chloride resin particles. In certain embodiments, the particles of the pelletized composition may have a similar size to that of the PVC, such as 80 to 120% of the average size of the polyvinyl chloride resin particles, or more preferably 90 to 110% of the average size of the polyvinyl chloride resin particles.

[0035] Preferably, the PVC composition comprises at least 25% by weight recycled PVC based on the total weight of the polyvinyl chloride resin. More preferably, the PVC composition comprises at least 40%, at least 50%, at least 60%, at least 70%, or at least 80% by weight recycled PVC based on the total weight of the polyvinyl chloride resin.

[0036] The polyvinyl chloride resin may also comprise virgin polyvinyl chloride resin, which may be present as a powder. When present, the virgin polyvinyl chloride resin is preferably present in a mixture with recycled polyvinyl chloride resin. The mixture of polyvinyl chloride resin may comprise both powder and particles of polyvinyl chloride resin. When such mixtures are used, a mixture of powdered processing aids and the particles of the pelletized composition comprising the high molecular weight processing aid may be used. Alternatively, the processing aid may be solely provided by the particles of the pelletized composition comprising the high molecular weight processing aid.

[0037] The present invention also relates to articles made from polyvinyl chloride resin compositions having the particles of the pelletized composition comprising the high molecular weight processing aid according to embodiments described above.

[0038] Another aspect of the present invention relates to a method of preparing a polyvinyl chloride composition comprising blending a polyvinyl chloride resin with particles of the pelletized composition comprising the high molecular weight processing aid. The particles of the pelletized composition comprising the high molecular weight processing aid can be incorporated at high concentrations which is let down into the bulk polyvinyl chloride resin during an extrusion process.EXAMPLES

[0039] To prepare Examples 1 to 3, particles of a composition comprising 100 wt% of a high molecular weight processing aid, SURECEL™ 467 (The Dow Chemical Company) were prepared. Particles were made by compacting powdered SURECEL™ 467 and breaking the compacted powder to form particles having an average particle size (D50) of 2 mm. Control Sample 1 was made from uncompacted powdered SURECEL™ 467 and used to determine degradation of the molecular weight. Examples 4 to 6 and Control Sample 2 were prepared in a similar manner using Paraloid™ 445. Examples 1 and 4 were compacted at a pressure of 5 ksi, Examples 2 and 5 were compacted at a pressure of 25 ksi, and Examples 3 and 6 were compacted at a pressure of 30 psi.

[0040] Gel permeation chromatograph (GPC) was used to determine the molecular weight of the high molecular weight processing aid. The GPC data is shown below in Table 1.Table 1What is claimed is:

Claims

1. A pelletized composition comprising: a high molecular weight processing aid, wherein the high molecular weight processing aid is present in an amount ranging from 50 to 100 wt% relative to the total weight of the composition; and one or more additional components selected from the group consisting of lubricants, heat stabilizers, antioxidants, fillers, and coloring agents, wherein the one or more additional components is present in an amount ranging from 0 to 50 wt% relative to the total weight of the composition; wherein the composition does not comprise a carrier resin; and wherein the composition is in the form of particles having a D50 particle size ranging from 1 to 30 mm and a dlO particle size of at least 50% of the D50 particle size .

2. The composition of claim 1 wherein the high molecular weight processing aid is a polymer or copolymer comprising monomers selected from vinyl aromatic, (meth)acrylonitrile, and alkyl (meth) acrylate monomers.

3. The composition of claim 1 or 2 wherein the high molecular weight processing aid is a copolymer comprising alkyl (meth)acrylate monomers.

4. The composition of claim 3 wherein the high molecular weight processing aid is a copolymer comprising methyl methacrylate and at least one monomer selected from alkyl acrylate monomers.

5. The composition of claim 4 wherein the alkyl acrylate monomers are selected from ethyl acrylate, butyl acrylate, or 2-ethyl hexyl acrylate.

6. The composition of any of the preceding claims wherein the high molecular weight processing aid has a weight average molecular weight of at least 5,000,000 g / mol.

7. The composition of any of the preceding claims wherein the high molecular weight processing aid has a weight average molecular weight of at least 10,000,000 g / mol.

8. The composition of any of the preceding claims wherein high molecular weight processing aid is present in an amount ranging from 70 to 100 wt% relative to the total weight of the composition.

9. The composition of any one of the preceding claims, wherein the high molecular weight processing aid is present in an amount ranging from 90 to 100 wt% relative to the total weight of the composition.

10. A polyvinyl chloride composition comprising a polyvinyl chloride resin and the composition according to any of the preceding claims.

11. The polyvinyl chloride composition according to claim 10 wherein the polyvinyl chloride resin comprises recycled polyvinyl chloride resin.

12. The polyvinyl chloride composition according to claim 11 wherein the polyvinyl chloride resin comprises a blend of recycled polyvinyl chloride resin and virgin polyvinyl chloride resin.

13. The polyvinyl chloride composition according to any one of claims 11 or 12, wherein the recycled polyvinyl chloride resin is in the form of particles having an average particle size ranging from 0.5 to 10 times the average particle size of the particles of the pelletized composition.

14. An article formed from the composition according to any one of claims 10 to 13.

15. A method of preparing a polyvinyl chloride composition comprising blending a polyvinyl chloride resin and the composition according to any one of claims 1 to 9.

Images