High molecular weight acrylic processing aid concentrate for thermoplastic processing

Abstract

A pelletized composition comprising a high molecular weight processing aid and one or more optional additional components is disclosed. 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 contain a carrier resin. The pelletized composition is in the form of particles having a D50 particle size in the range of 1 to 30 mm and a D10 particle size at least 50% of the D50 particle size.

Description

Technical Field

[0001] The field of the present invention is high molecular weight acrylic processing aids concentrates.

Background Art

[0002] Polyvinyl chloride (PVC) is widely used in a variety of applications including architectural and construction products such as fences, siding, decks, trim boards, partition boards, window frames, door sills, and doors. Unused PVC polymer resin is generally supplied in powder form. PVC is typically formulated by dry blending with other components, which are also typically in powder form, and heat processed into the final product by melt extrusion.

[0003] Acrylic processing aids are generally one of the powder components incorporated into PVC formulations. Acrylic processing aids are typically added to PVC in parts per hundred resin (phr) per 100 parts of resin.

[0004] Due to environmental sustainability, there is increasing interest in reusing and recycling materials containing PVC to increase the amount of consumed or industrially used waste in the material stream. When incorporated into PVC formulations, consumed or industrially used scrap PVC is typically mixed with unused PVC powder. However, problems arise with the use of scrap PVC.

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

[0006] Similarly, when pulverized PVC particles, typically larger than 35 mesh (500 microns), and more commonly larger than 18 mesh (1 mm), are mixed with commercially available powdered processing aids having an average particle size of approximately 50-500 microns, problems arise due to the size difference between the pulverized PVC and the processing aids. As with mixing pulverized PVC with unused PVC powder, mixing pulverized PVC with powdered processing aids results in particle separation, leading to an uneven mixture before extrusion.

[0007] When using scrap PVC, another problem arises due to the fact that many PVC formulations already contain additives from the original formulation. Since these additives are not removed during the grinding process, scrap PVC particles have a different composition than unused PVC powder.

[0008] International Publication No. WO2022 / 072220(A1) discloses a composition containing a high molecular weight processing aid having an average particle size of at least 2 mm. However, the composition disclosed in International Publication No. WO2022 / 072220(A1) requires the presence of a carrier resin as either a passive or active component of the composition.

[0009] The presence of a carrier can cause problems in the use of scrap PVC due to variations in composition. When using scrap PVC, it is desirable to better control the composition when adding processing aids or other components.

[0010] This invention aims to solve one or more of the problems described above. [Overview of the project]

[0011] Disclosed herein are pelletized compositions 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 colorants. The high molecular weight processing aid is present in an amount ranging from 50 to 100% by weight of 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 of the total weight of the composition. The composition does not contain 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.

[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 colorants, wherein the high molecular weight processing aid is present in an amount ranging from 50 to 100% by weight of 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 of the total weight of the composition. The pelletized composition does not contain 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.

[0013] Methods for preparing polyvinyl chloride compositions and articles manufactured therefrom are also disclosed. [Modes for carrying out the invention]

[0014] An improved processing aid for use in polyvinyl chloride compositions is disclosed herein. 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 in the range of 1 to 30 mm and a d10 particle size of at least 50% of the D50 particle size. The pelletized composition does not contain a carrier resin.

[0015] As used herein, “pelletized composition” is a composition comprising particles in the form of aggregated, clustered, grouped, combined, solidified, or aggregated smaller particles. For example, a pelletized composition may be formed by first drying the composition to form a powder, and then further processing the powder to form larger aggregates 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 a particle is the ratio of the longest diameter to the shortest diameter. Particles may have any shape, including, for example, spherical, cylindrical, elliptical, cubic, prismatic, or irregular. As used herein, the terms “D10” and “D50” particle size values ​​refer to the size of a pelletized composition in which 10% and 50% of the mass, respectively, are occupied by having a diameter less than or equal to the specified value. Thus, the D10 value is the particle size where 10% by weight of all particles in the pelletized composition is smaller than the specified particle size. The D50 value is the “median particle size by weight” where 50% by weight of all particles in the pelletized composition is smaller than the specified particle size.

[0018] Suitable high molecular weight polymer processing aids useful in the present invention include polymers and copolymers containing vinyl aromatics, (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 monomers and alkyl acrylate monomers.

[0019] Preferably, the high molecular weight processing aid is a copolymer containing an alkyl (meth)acrylate monomer. For example, the high molecular weight processing aid is a copolymer containing methyl (meth)acrylate. The methyl (meth)acrylate copolymer may contain monomers selected from other alkyl (meth)acrylate monomers such as ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate. An exemplary high molecular weight processing aid includes a copolymer containing a majority (i.e., at least 50% by weight of the total weight of the high molecular weight processing aid) of methyl methacrylate ("MMA") and a small amount (i.e., less than 50% by weight of the total weight of the high molecular weight processing aid) of an alkyl acrylate such as ethyl acrylate, butyl acrylate, or 2-ethylhexyl acrylate.

[0020] High molecular weight processing aids may include core-shell type processing aids that combine the functionality of external lubricants and processing aids. These "lubricating processing aids" provide the typical processing performance characteristics of acrylic processing aids, but have the added benefit of external lubricant functionality that improves flow and machine uptime by significantly reducing the adhesion of molten polyvinyl chloride resin to the hot metal surface of the processing equipment.

[0021] Commercially available high molecular weight processing aids are available from The Dow Chemical Company (Midland, Michigan) under the trade names 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% by weight relative to the total weight of the pelletized composition. For example, the high molecular weight processing aid may 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 may be present in an amount of 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 is present in an amount ranging from 60% to 100% by weight, more preferably 70% to 100%, even more preferably 80% to 100%, and even more preferably 90% to 100% by weight relative to the total weight of the pelletized composition. In a preferred embodiment, the high molecular weight processing aid constitutes 100% by weight of the total weight of the pelletized composition. In other words, the pelletized composition consists of a high molecular weight processing aid.

[0023] The composition may further contain one or more additional components, including lubricants, heat stabilizers, antioxidants, fillers, colorants, and other additives. If present, these additional components may be present in amounts exceeding 0% to 50% by weight relative to the total weight of the pelletized composition, for example, exceeding 0% to 40% by weight, 1% to 35% by weight, 2% to 30% by weight, or 5% to 25% by weight relative to the total weight of the pelletized composition.

[0024] Suitable lubricants that can be used in the composition include internal and external lubricants, as well as lubricants having a balance between internal and external lubrication properties. Generally, external lubricants determine the behavior of high-temperature plastic compounds at interfaces with other materials, such as delaying melting / gelling and reducing sticking and friction, while internal lubricants affect rheological processes within the polymer phase, such as providing lubrication between polymer chains and improving melt flow. Examples of lubricants include, for example, esters such as monoglycerol esters, hydrocarbon waxes such as paraffin wax, polyethylene wax, and oxidized polyethylene wax, fatty acids such as esters, stearyl alcohol, and stearic acid, fatty acid amides such as ethylenebis-stearamide (i.e., two C16-C18 alkyl groups covalently bonded to a central polar amide group), soaps, and stearates such as calcium stearate. Suitable external lubricants include, but are not limited to, long-chain montanic acids (i.e., long-chain C28-C32 alkyl groups covalently bonded to polar groups such as carboxylic acids), paraffins and hydrocarbons having short-branched alkyl groups, n-paraffins having long-chain hydrocarbons, and polyethylene waxes having very long-chain hydrocarbon chains with several branches. Suitable lubricants that provide a balance between internal and external lubrication include calcium-partially saponified synthetic fatty acids and long-chain montan ester types (e.g., Wax OP and Wax E available from American Hoechst Corp. (Mountainside, NJ)). Further information on lubricants for PVC can be found in the review by McMurrer, MC, 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. An exemplary antioxidant is one sold by Adeka under the ADK STAB brand.

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

[0027] The pelletized composition of the present invention does not contain a carrier resin. The carrier resin includes both a passive carrier resin and an active carrier resin that may have some activity as a processing aid. Thus, the pelletized composition of the present invention does not contain a carrier resin, such as immiscible polymers such as polyethylene, polyethylene terephthalate, polypropylene, and inorganic materials such as talc, calcium carbonate, and fibers, or an active carrier resin such as terpolymers such as ethylene terpolymers and polyethylene wax.

[0028] International Publication No. WO2022 / 072 (A1) discloses a composition comprising a high molecular weight processing aid and a carrier resin. The inventors have surprisingly found that a pelletized composition can be prepared without the presence of a carrier resin.

[0029] The pelletized composition of the present invention can be prepared, for example, by blending a high molecular weight processing aid and, if present, one or more additional components as powders, and then processing the blended composition to form larger particles. The inventors have found that special processing is required to form larger particles in order to avoid a decrease in the molecular weight of the processing aid that can occur in a process that applies shear forces during processing. For example, the particles of the pelletized composition can be formed by consolidation, compression, or low shear extrusion.

[0030] The composition of the present invention exists in the form of particles having a D50 particle size of at least 18 mesh or 1 mm. For example, the particles may have an average particle size of at least 10 mesh (2 mm), at least 8 mesh (2.38 mm), at least 6 mesh (3.36 mm), or at least 5 mesh (4 mm). When used with finely ground resin, the average particle size of the composition may be smaller than 10 mesh. Preferably, the D50 particle size of the pelletized composition particles is in the range of 1 mm to 30 mm, more preferably 2 mm to 20 mm.

[0031] The D10 particle size of the pelletized composition particles is 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%, and even more preferably at least 80%. When the D10 particle size is close to the D50 particle size, there are fewer small particles present in the pelletized composition, which is thought to increase the likelihood of stratification or separation of the composition in which the pelletized composition is used.

[0032] The pelletized composition may contain, consist of, or be essentially composed of 50 to 100% by weight of a high molecular weight processing aid and 0 to 50% by weight of one or more additional components selected from the group consisting of lubricants, heat stabilizers, antioxidants, fillers, and colorants, the weight percentages being based on the total weight of the composition. As used herein, the term "essentially composed of" means that the pelletized composition contains less than 5% by weight of any components other than the high molecular weight processing aid and one or more additional components selected from the group consisting of lubricants, heat stabilizers, antioxidants, fillers, and colorants. Preferably, the pelletized composition contains less than 2% by weight of any components other than the high molecular weight processing aid and one or more additional components selected from the group consisting of lubricants, heat stabilizers, antioxidants, fillers, and colorants.

[0033] Polyvinyl chloride (PVC) compositions can be prepared by blending polyvinyl chloride resin with particles of a pelletized composition containing a high molecular weight processing aid. The pelletized composition containing the high molecular weight processing aid may be present in the PVC composition in an amount ranging from 0.5 to 20 parts (phr) per 100 parts of resin, for example. For example, the pelletized composition containing the high molecular weight processing aid may be present in the PVC composition in an amount ranging from 1 to 15 phr or 2 to 10 phr.

[0034] Preferably, the polyvinyl chloride resin includes recycled PVC. As used herein, “recycled PVC” refers to used or industrially used scrap, i.e., unused PVC. Typically, recycled PVC is processed by grinding articles made of polyvinyl chloride. The grinding process yields polyvinyl chloride particles having, for example, an average particle size in the range of 1 mm to 30 mm. Preferably, the recycled PVC has an average particle size of 0.5 to 15 times, more preferably 1 to 10 times, and even more preferably 1 to 5 times, the average particle size of the pelletized composition. Preferably, the particles of the pelletized composition containing a 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, if the average particle size of the polyvinyl chloride resin is 20 mm, the average particle size of the particles containing the high molecular weight processing aid is at least 2 mm. More preferably, the particles of the composition containing 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. More preferably, the particles of the composition containing the high molecular weight processing aid have an average size of at least 30% of the average size of the polyvinyl chloride resin particles, and even more preferably, the particles of the composition containing the high molecular weight processing aid have an average size of 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 size similar to that of PVC, for example, 80-120% of the average size of the polyvinyl chloride resin particles, or more preferably 90-110% of the average size of the polyvinyl chloride resin particles.

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

[0036] The polyvinyl chloride resin may also contain unused polyvinyl chloride resin, which may exist as a powder. If present, the unused polyvinyl chloride resin is preferably present in a mixture with recycled polyvinyl chloride resin. The polyvinyl chloride resin mixture may contain both powder and particles of polyvinyl chloride resin. When using such a mixture, a mixture of a powdered processing aid and particles of a pelletized composition containing a high molecular weight processing aid may be used. Alternatively, the processing aid may be provided solely by particles of a pelletized composition containing a high molecular weight processing aid.

[0037] The present invention also relates to an article made from a polyvinyl chloride resin composition having particles of a pelletized composition containing a high molecular weight processing aid according to the above embodiments.

[0038] Another aspect of the present invention relates to a method for preparing a polyvinyl chloride composition, comprising blending a polyvinyl chloride resin with particles of a pelletized composition containing a high molecular weight processing aid. The particles of the pelletized composition containing the high molecular weight processing aid can be incorporated at high concentrations, which are diluted with the bulk polyvinyl chloride resin during the extrusion process. [Examples]

[0039] To prepare Examples 1-3, particles of a composition containing 100% by weight of the high molecular weight processing aid, SURECEL® 467 (The Dow Chemical Company), were prepared. The particles were produced by compressing powdered SURECEL® 467 and crushing the compressed powder to form particles with an average particle size (D50) of 2 mm. Control sample 1 was prepared from uncompressed powdered SURECEL® 467 and used to determine the reduction in molecular weight. Examples 4-6 and control sample 2 were similarly prepared using Paraloid® 445. Examples 1 and 4 were compressed at a pressure of 5 ksi, Examples 2 and 5 were compressed at a pressure of 25 ksi, and Examples 3 and 6 were compressed at a pressure of 30 psi.

[0040] The molecular weight of the high molecular weight processing aid was determined using gel permeation chromatography (GPC). The GPC data is shown in Table 1 below.

[0041] [Table 1]

Claims

1. A pelletized composition, A high molecular weight processing aid present in an amount ranging from 50% to 100% by weight relative to the total weight of the composition, The composition comprises one or more additional components selected from the group consisting of lubricants, heat stabilizers, antioxidants, fillers, and colorants, present in an amount ranging from 0 to 50% by weight relative to the total weight of the composition. The composition does not contain a carrier resin. The composition is in the form of particles having a D50 particle size in the range of 1 to 30 mm and a d10 particle size that is at least 50% of the D50 particle size.

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

3. The composition according to claim 1 or 2, wherein the high molecular weight processing aid is a copolymer containing an alkyl (meth)acrylate monomer.

4. The composition according to 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 according to claim 4, wherein the alkyl acrylate monomer is selected from ethyl acrylate, butyl acrylate, or 2-ethylhexyl acrylate.

6. The composition according to any one of claims 1 to 5, wherein the high molecular weight processing aid has a weight-average molecular weight of at least 5,000,000 g / mol.

7. The composition according to any one of claims 1 to 6, wherein the high molecular weight processing aid has a weight-average molecular weight of at least 10,000,000 g / mol.

8. The composition according to any one of claims 1 to 7, wherein the high molecular weight processing aid is present in an amount ranging from 70 to 100% by weight relative to the total weight of the composition.

9. The composition according to any one of claims 1 to 8, wherein the high molecular weight processing aid is present in an amount ranging from 90 to 100% by weight relative to the total weight of the composition.

10. A polyvinyl chloride composition comprising a polyvinyl chloride resin and the composition described in any one of claims 1 to 9.

11. The polyvinyl chloride composition according to claim 10, wherein the polyvinyl chloride resin includes 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 unused polyvinyl chloride resin.

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

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

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

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