Polyvinyl chloride resin composition

Abstract

To provide a polyvinyl chloride resin composition that includes a Ca-Zn type stabiliser and allows production of a foamed body with superior foaming performance and reduced specific gravity.SOLUTION: A polyvinyl chloride resin composition comprises a polyvinyl chloride-based resin, a Ca-Zn type stabiliser, a thermally decomposable chemical foaming agent, and an acrylic processing aid, wherein the decomposition initiation temperature of the thermally decomposable chemical foaming agent is 160°C or more, the weight-average molecular weight of the acrylic processing aid is 500,000 or less, and the composition contains 2 to 10 pts.mass of the acrylic processing aid per 100 pts.mass of the polyvinyl chloride-based resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a vinyl chloride resin composition capable of forming a foam having a low specific gravity. [Background technology]

[0002] Molded products of foamed rigid polyvinyl chloride resin are lightweight and have excellent flame retardancy and other physical properties, and are therefore used in a variety of building materials (for example, Patent Documents 1 and 2). Patent Document 1 proposes a resin powder containing a heat-decomposable foaming component in the pores of a suspension-type porous polyvinyl chloride resin to form a foamed resin layer with fine, uniform pores, with the aim of using the powder as a backing layer for tile carpets. Patent Document 2 proposes a vinyl chloride resin composition that does not use azodicarbonamide (ADCA) but adds 4,4'-oxybisbenzenesulfonylhydrazide (OBSH) as a foaming agent, in order to reduce the yellowness caused by the foaming agent, with the use of foam wallpaper in mind. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-150113 [Patent Document 2] Japanese Patent Application Publication No. 2018-188774 Summary of the Invention [Problem to be solved by the invention]

[0004] Inorganic stabilizers are often added to vinyl chloride resin compositions. Traditionally, lead-based stabilizers were used, but the use of lead is restricted by the RoHS Directive. Therefore, lead-based stabilizers are being replaced with other types of stabilizers. However, different stabilizers have different processability, so processing aids must be adjusted for each type of stabilizer.

[0005] The present invention provides a vinyl chloride resin composition that contains a Ca-Zn stabilizer, has excellent foaming properties, and is capable of forming foams with a low specific gravity. [Means for solving the problem]

[0006] [1] A vinyl chloride resin composition comprising a vinyl chloride resin, a Ca-Zn stabilizer, a thermally decomposable chemical foaming agent, and an acrylic processing aid, wherein the thermally decomposable chemical foaming agent has a decomposition onset temperature of 160°C or higher, the acrylic processing aid has a weight-average molecular weight of 500,000 or less, and the vinyl chloride resin composition contains 2 to 10 parts by mass of the acrylic processing aid per 100 parts by mass of the vinyl chloride resin. [2] The vinyl chloride resin composition according to [1], wherein the thermally decomposable chemical blowing agent is an azodicarbonamide-based blowing agent, and the vinyl chloride resin composition contains 0.8 to 3 parts by mass of the thermally decomposable chemical blowing agent per 100 parts by mass of the vinyl chloride resin. [3] The vinyl chloride resin composition according to [1] or [2], further comprising an acrylic processing aid having a weight-average molecular weight of 2,000,000 or more. [4] The vinyl chloride resin composition according to [3], further comprising 2 to 10 parts by mass of the acrylic processing aid having a weight-average molecular weight of 2,000,000 or more per 100 parts by mass of the vinyl chloride resin. [5] The vinyl chloride resin composition according to [3] or [4], wherein the total content of the content M1 of the first acrylic processing aid having a weight-average molecular weight of 500,000 or less and the content M2 of the second acrylic processing aid having a weight-average molecular weight of 2,000,000 or more is 4 to 12 parts by mass per 100 parts by mass of the vinyl chloride resin. [6] The vinyl chloride resin composition according to [5], wherein the mass content ratio represented by (the content M1 / the content M2) is 0.5 to 2.0. [Effects of the Invention]

[0007] The vinyl chloride resin composition of the present invention combines a Ca-Zn stabilizer with a specific thermal decomposition type chemical foaming agent and a processing aid, making it easy to form low-specific-gravity foams. DETAILED DESCRIPTION OF THE INVENTION

[0008] <Vinyl chloride resin composition> A first aspect of the present invention is a vinyl chloride resin composition (PVC composition) containing a vinyl chloride resin, a Ca—Zn stabilizer, a thermal decomposition type chemical foaming agent, and an acrylic processing aid.

[0009] [Vinyl chloride resin] The vinyl chloride resin included in this embodiment may be a vinyl chloride homopolymer (PVC) or a copolymer. Examples of copolymerizable monomers include ethylene, propylene, acrylonitrile, vinyl acetate, maleic acid or its ester, acrylic acid or its ester, methacrylic acid or its ester, and vinylidene chloride.

[0010] The vinyl chloride resin is preferably a vinyl chloride homopolymer. When it is a copolymer, the content of repeating units other than vinyl chloride is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of repeating units derived from vinyl chloride. The vinyl chloride resin of this embodiment may be chlorinated after the resin is formed.

[0011] The average degree of polymerization of the vinyl chloride resin is not particularly limited, but is preferably, for example, from 700 to 4000, more preferably from 800 to 3000, and even more preferably from 800 to 2000. When the average degree of polymerization is within the above preferred range, it becomes easy to obtain hardness suitable for various building material applications. Here, the average degree of polymerization of the vinyl chloride resin is the average degree of polymerization measured in accordance with JIS K6720-2. The average degree of polymerization is calculated from the K value. The K value is a value measured in accordance with JIS K7367-2 (ISO1628-2).

[0012] The content of the vinyl chloride resin relative to the total mass of the PVC composition of this embodiment is preferably 65 to 92 mass%, more preferably 70 to 90 mass%, even more preferably 75 to 88 mass%, and most preferably 80 to 85 mass%. Within these preferred ranges, the blending ratio with other components becomes appropriate, making it easy to obtain a foam with a low specific gravity.

[0013] The PVC composition of this embodiment may contain a resin other than the vinyl chloride resin. From the viewpoint of fully achieving the effects of the present invention, the content of the resin other than the vinyl chloride resin is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of the vinyl chloride resin.

[0014] [Ca-Zn stabilizer] The stabilizer included in this embodiment is a calcium-zinc stabilizer, which contains calcium and zinc. As the Ca-Zn stabilizer, commercially available ones that are blended with vinyl chloride resins can be used. The Ca-Zn stabilizer included in this embodiment may be one type or two or more types. The content of the Ca-Zn stabilizer is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 8.0 parts by mass, even more preferably 1.0 to 6.0 parts by mass, and most preferably 2.0 to 4.0 parts by mass, relative to 100 parts by mass of the vinyl chloride resin. Within these preferred ranges, a foam having a low specific gravity can be more easily formed.

[0015] [Thermal decomposition type chemical foaming agent] The thermal decomposition type chemical blowing agent included in this embodiment only needs to have a decomposition initiation temperature of 160°C or higher, and is preferably an azodicarbonamide-based blowing agent (ADCA-based blowing agent) because heat control during processing is easy. The azodicarbonamide-based blowing agent may be azodicarbonamide or a modified azodicarbonamide in which a portion of the azodicarbonamide is chemically modified. ADCA-based blowing agents with sensitive thermal decomposition initiation temperatures are commercially available, and a good example is the Cellmike series ADCA-based blowing agent manufactured by Sankyo Kasei Co., Ltd. The thermal decomposition type chemical blowing agent included in this embodiment may be one type or two or more types.

[0016] In this embodiment, when an ADCA foaming agent is used, the content thereof is preferably 0.8 to 3.0 parts by mass, more preferably 0.8 to 2.5 parts by mass, and even more preferably 0.8 to 2.0 parts by mass, relative to 100 parts by mass of the vinyl chloride resin. Within these preferred ranges, a foam with a low specific gravity can be more easily formed.

[0017] [Acrylic processing aids] The acrylic processing aid included in this embodiment is a high-molecular-weight (meth)acrylic polymer, and the long chains of its molecules become entangled with the molecules of the matrix resin PVC, creating a pseudo-crosslinked state and imparting melt elasticity. As an acrylic processing aid, the P type of Metablen (registered trademark) manufactured by Mitsubishi Chemical Corporation is preferred. They are sold in categories based on weight-average molecular weight, and acrylic processing aids in the desired molecular weight range can be purchased. The acrylic processing aid included in this embodiment may be one type or two or more types.

[0018] The first acrylic processing aid may have a weight average molecular weight of 500,000 or less. The upper limit of the weight average molecular weight of the first acrylic processing aid is preferably 450,000 or less, more preferably 400,000 or less, and even more preferably 350,000 or less. The lower limit of the weight average molecular weight of the first acrylic processing aid is preferably 50,000 or more, more preferably 100,000 or more, and even more preferably 200,000 or more. Within these preferred ranges, processability is improved, and a foam having a low specific gravity can be more easily formed.

[0019] The content of the first acrylic processing aid included in this embodiment is preferably 2.0 to 10 parts by mass, more preferably 2.0 to 8.0 parts by mass, even more preferably 2.0 to 6.0 parts by mass, and most preferably 3.0 to 5.0 parts by mass, relative to 100 parts by mass of the vinyl chloride resin. Within these preferred ranges, processability is improved, and a foam having a low specific gravity can be more easily formed.

[0020] The second acrylic processing aid may have a weight average molecular weight of 2,000,000 or more. The lower limit of the weight average molecular weight of the second acrylic processing aid is preferably 2.3 million or more, more preferably 2.6 million or more, and even more preferably 3 million or more. The upper limit of the weight average molecular weight of the second acrylic processing aid is preferably 4,000,000 or less, more preferably 3,700,000 or less, and even more preferably 3,400,000 or less. Within these preferred ranges, processability is improved, and a foam having a low specific gravity can be more easily formed.

[0021] The content of the second acrylic processing aid in this embodiment is preferably 2.0 to 10 parts by mass, more preferably 2.0 to 8.0 parts by mass, even more preferably 2.0 to 6.0 parts by mass, and most preferably 3.0 to 5.0 parts by mass, relative to 100 parts by mass of the vinyl chloride resin. Within these preferred ranges, processability is improved, and a foam having a low specific gravity can be more easily formed.

[0022] In this embodiment, when first and second acrylic processing aids are contained, the total content of the first acrylic processing aid M1 and the second acrylic processing aid M2 is preferably 4.0 to 12 parts by mass, more preferably 5.0 to 11 parts by mass, even more preferably 6.0 to 10 parts by mass, and most preferably 7.0 to 9.0 parts by mass, per 100 parts by mass of the vinyl chloride resin. Within these preferred ranges, processability is improved, and a low-specific-gravity foam can be more easily formed.

[0023] In this embodiment, when the first and second acrylic processing aids are contained, the mass-based content ratio represented by (the content M1 / the content M2) is preferably 0.5 to 2.0, and also preferably in the ranges of 0.6 to 1.8, 0.7 to 1.6, 0.8 to 1.4, 0.9 to 1.2, and 0.9 to 1.1. Within these preferred ranges, processability is further improved, and a foam with a low specific gravity can be more easily formed.

[0024] The PVC composition of this embodiment may contain processing aids other than the above-mentioned acrylic processing aids, provided that the gist of the present invention is not impaired. Examples of other processing aids include fatty acid amide lubricants such as stearic acid amide and oleic acid amide, waxes such as paraffin wax, polyolefin wax, ester wax, montanic acid wax, and polyethylene wax, higher fatty acids such as stearic acid and behenic acid, higher alcohols such as stearyl alcohol and cetyl alcohol, fatty acid ester lubricants such as butyl stearate and stearic acid monoglyceride, metal soaps such as calcium stearate and magnesium stearate, and oils such as silicone oil and procel oil.

[0025] The total content of other processing aids is preferably 0.1 to 8.0 parts by mass, more preferably 1.0 to 5.0 parts by mass, and even more preferably 1.0 to 3.0 parts by mass, relative to 100 parts by mass of the vinyl chloride resin.

[0026] [Plasticizer] The PVC composition of this embodiment can form a rigid vinyl chloride resin foam, so it does not need to contain a plasticizer, but a plasticizer may be added if necessary.

[0027] As the plasticizer, those generally used as plasticizers for vinyl chloride resins can be used. Specific examples of the plasticizer include epoxy plasticizers. Epoxy plasticizers are plasticizers having one or more epoxy groups in the molecule, and may have one or more ester groups in addition to the epoxy groups. Examples of epoxy plasticizers include those obtained by epoxidizing vegetable oils, such as epoxidized soybean oil and epoxidized linseed oil (both manufactured by Sankyo Kasei Co., Ltd.).

[0028] When the PVC composition of this embodiment contains a plasticizer, the content thereof is preferably 0.1 to 8.0 parts by mass, more preferably 0.3 to 4.0 parts by mass, even more preferably 0.6 to 2.0 parts by mass, and most preferably 0.9 to 1.5 parts by mass, relative to 100 parts by mass of the vinyl chloride resin. Within these preferred ranges, the processability is further enhanced, and a low-density foam can be more easily formed.

[0029] [Filler] A filler may be blended into the PVC composition of this embodiment in order to enhance the mechanical strength of the molded product. As the filler, those generally used as fillers for resin compositions can be applied. As specific fillers, carbonates are preferable. Examples of carbonates include magnesium carbonate, calcium carbonate, and dawsonite. Among these, from the viewpoint of further enhancing the molding processability, heavy calcium carbonate obtained by pulverizing limestone is preferable.

[0030] When the PVC composition of this embodiment contains a filler, its content is preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass, still more preferably 4 to 10 parts by mass, and most preferably 6 to 8 parts by mass with respect to 100 parts by mass of the vinyl chloride-based resin. Within these preferred ranges, the processability is further enhanced, and a low-density foam can be more easily formed.

[0031] [Other additives] In the PVC composition of this embodiment, optional additives such as ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, antibacterial agents, and pigments may be blended within a range that does not impair the effects of the present invention.

[0032] [Method for producing PVC composition] The method for producing the PVC composition of this embodiment is not particularly limited, and it can be obtained by mixing and kneading by a conventional method so that each component becomes uniform in the composition. If mixing and kneading are performed at a temperature lower than the temperature at which the decomposition of the thermal decomposition type chemical foaming agent starts, an unfoamed PVC composition can be obtained.

[0033] [Form of PVC composition] Specific forms of the PVC composition of this embodiment may be compounds, pellets, beads, or powders that are easily subjected to another molding process, or molded products molded by known molding methods such as press molding, injection molding, and extrusion molding. The molded article is not particularly limited, and examples thereof include automobile interior parts and various building materials. [Example]

[0034] The present invention will be specifically explained below by showing examples, but the present invention is not limited to these examples.

[0035] The details of the raw materials listed in Table 1 are as follows: "PVC with a degree of polymerization of 800" is TK-800 manufactured by Shin-Etsu Chemical Co., Ltd. The "Ca-Zn stabilizer" is LHR-402FM manufactured by Sakai Chemical Industry Co., Ltd., and is a Pb-free heat stabilizer. "Epoxidized soybean oil" is Chemicizer SE-100 manufactured by Sanwa Synthetic Chemical Industry Co., Ltd., and is an epoxy-based plasticizer. "Calcium carbonate" is Whiten-SB manufactured by Shiraishi Calcium Co., Ltd., and is a filler. "Acrylic processing aid (1)" is Mitsubishi Chemical's Metablen P-530A, a polymer with a weight-average molecular weight of 3.1 million. "Acrylic processing aid (2)" is Mitsubishi Chemical's Metablen P-570A, a polymer with a weight-average molecular weight of 270,000. "Acrylic processing aid (3)" is Mitsubishi Chemical's Metablen P-501A, a polymer with a weight-average molecular weight of 800,000. "ADCA-based foaming agent (1)" is Cellmike 172-C manufactured by Sankyo Kasei Co., Ltd., an ADCA-based foaming agent with a decomposition starting temperature of 165°C. It is known that its decomposition temperature is extremely sensitive, and when heated at a rate of 5°C / min, it shows almost no decomposition up to 160°C, begins to decompose at 165°C, and decomposition accelerates rapidly at 170°C. "ADCA-based foaming agent (2)" is Cellmike CAP-500 manufactured by Sankyo Kasei Co., Ltd., an ADCA-based foaming agent with a decomposition starting temperature of 150°C. It is known that its decomposition temperature is very sensitive, and when heated at a rate of 5°C / min, it hardly decomposes up to 140°C, but decomposition begins suddenly at 145-150°C. The "fatty acid ester lubricant" is Rokiol G32 manufactured by Emery Oleochemicals, and is a general-purpose lubricant for enhancing the lubricity against the die of an extruder or the like.

[0036] <Preparation of PVC Composition> Each raw material was mixed in the amounts (parts by mass) shown in Table 1, and kneaded at temperature conditions of 130 to less than 160 °C using a 30 mm single-screw extruder (die: φ6 mm round bar, screw rotation speed: 30 rpm) to produce a compound of a vinyl chloride resin composition. For example, in Example 1, based on 100 parts by mass of PVC, 3 parts by mass of a Ca-Zn-based stabilizer, 1 part by mass of epoxidized soybean oil, 7 parts by mass of calcium carbonate, 4 parts by mass of a first acrylic processing aid, 4 parts by mass of a second acrylic processing aid, 1 part by mass of an ADCA-based foaming agent, and 1 part by mass of a fatty acid ester lubricant were blended in a total of 121 parts by mass to obtain an unfoamed PVC composition.

[0037] <Confirmation of Foaming Property of PVC Composition> The compound of the PVC composition obtained above was charged into the above single-screw extruder and extruded while raising the temperature from 150 °C to 180 °C to obtain a foam of the PVC composition. The specific gravity of the obtained foam was measured according to "8.3.1 When the liquid is used as the standard substance" of "8 Measurement method of density and specific gravity by the immersion method in liquid" of JIS Z 8807:2012 (Method for measuring density and specific gravity of solids), and the degree of foaming was confirmed.

[0038]

Table 1

[0039] In the PVC composition of the example according to the present invention, good foaming was achieved, and a low-specific gravity foam in a form reflecting good foaming could be formed. That is, a foam with a sufficiently low specific gravity was obtained. The specific gravity of the unfoamed PVC composition is 1.3 to 1.4. In Comparative Example 1, since it did not contain an acrylic processing aid having a weight average molecular weight of 500,000 or less, the decrease in specific gravity was insufficient. In Comparative Example 2, the acrylic processing aid having a weight-average molecular weight of 500,000 or less was contained in excess, and therefore the reduction in specific gravity was insufficient. In Comparative Example 3, the amount of the chemical foaming agent having a decomposition starting temperature of 160° C. or higher was small, and therefore the reduction in specific gravity was insufficient.

Claims

1. A vinyl chloride resin composition comprising a vinyl chloride resin, a Ca-Zn stabilizer, a thermal decomposition type chemical foaming agent, and an acrylic processing aid, the thermal decomposition type chemical foaming agent has a decomposition initiation temperature of 160°C or higher, The weight average molecular weight of the acrylic processing aid is 500,000 or less, A vinyl chloride resin composition comprising 2 to 10 parts by mass of the acrylic processing aid per 100 parts by mass of the vinyl chloride resin.

2. the thermal decomposition type chemical foaming agent is an azodicarbonamide foaming agent, 2. The vinyl chloride resin composition according to claim 1, comprising 0.8 to 3 parts by mass of the thermal decomposition type chemical foaming agent per 100 parts by mass of the vinyl chloride resin.

3. 3. The vinyl chloride resin composition according to claim 1, further comprising an acrylic processing aid having a weight-average molecular weight of 2,000,000 or more.

4. 4. The vinyl chloride resin composition according to claim 3, further comprising 2 to 10 parts by mass of the acrylic processing aid having a weight average molecular weight of 2,000,000 or more per 100 parts by mass of the vinyl chloride resin.

5. A content M1 of the first acrylic processing aid having a weight average molecular weight of 500,000 or less; The content M2 of the second acrylic processing aid having a weight average molecular weight of 2 million or more; The total content is 4 to 12 parts by mass per 100 parts by mass of the vinyl chloride resin. The vinyl chloride resin composition according to claim 4.

6. 6. The vinyl chloride resin composition according to claim 5, wherein a content ratio on a mass basis represented by (the content M1 / the content M2) is 0.5 to 2.0.

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