Plastisol composition

Abstract

To provide a plastisol composition exhibiting excellent processability and mechanical characteristics at low processing temperatures such as 80-100°C and having superior properties as a coating agent, especially for automotive underbody coatings and automotive sealants, and also to provide a use thereof.SOLUTION: A plastisol composition comprising at least a paste-processable vinyl chloride-vinyl acetate copolymer, a plasticizer, and a diluent, wherein the paste-processable vinyl chloride-vinyl acetate copolymer comprises 10-22 wt.% of vinyl acetate polymerized units and has an average degree of polymerization of 1000-3400, the weight ratio of the paste-processable vinyl chloride-vinyl acetate copolymer to the total weight of the paste-processable vinyl chloride-vinyl acetate copolymer, the plasticizer, and the diluent is 40-58 wt.%, and the weight ratio of the diluent to the total weight of the plasticizer and the diluent is 15-27 wt.%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a plastisol composition containing at least a vinyl chloride resin for paste processing, a plasticizer, and a diluent, and more particularly to a plastisol composition that is applicable to low-temperature processing and is useful as a coating agent, particularly for automobile underbody coatings and automobile sealants, and uses thereof. [Background technology]

[0002] To minimize environmental impact, measures to reduce carbon dioxide emissions and save energy are being implemented in the automotive underbody coating and sealant painting processes. As part of these efforts, there is a demand to reduce carbon dioxide emissions generated by the energy consumption of baking ovens in the painting process. To achieve energy savings and reduced carbon dioxide emissions, there is a need to lower the temperature of baking ovens. However, processing at low temperatures can cause a problem of deterioration in the mechanical properties of molded products, so there is a demand for coating agents that can be processed at low temperatures.

[0003] Vinyl chloride resins for paste processing (hereinafter sometimes abbreviated as "paste PVC") are generally prepared by kneading with plasticizers, fillers, stabilizers, and other compounding agents to prepare plastisols, which can be molded by heating. These resins are widely used in automobile underbody coatings and automobile sealants. As a paste PVC that can be gelled and melted at relatively low temperatures (specifically, 140°C) and has excellent mechanical strength, vinyl chloride / vinyl acetate copolymer resins, in which vinyl chloride is copolymerized with vinyl acetate, have been proposed (see, for example, Patent Document 1). Furthermore, as a plastisol composition that can achieve mechanical strength at processing temperatures of 100 to 120°C, a blend of vinyl chloride-vinyl acetate copolymer resin and (meth)acrylic resin, with a blocked isocyanate added as an adhesive, has been proposed (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-076477 [Patent Document 2] Patent Publication No. 2021-011525 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there is an ever-increasing demand in industry, particularly in the automotive industry, for a reduction in energy consumption in manufacturing processes, and coating agents that can be processed at lower temperatures, particularly at temperatures below 100°C, are in demand. However, the proposals in Patent Documents 1 and 2 did not specifically address the processability, mechanical properties, etc., at baking temperatures below 100°C.

[0006] Therefore, the present invention aims to provide a plastisol composition that has excellent processability and mechanical properties when processed at low temperatures (more specifically, 80 to 100°C) and has excellent properties as a coating agent, particularly for use as an automobile underbody coating or an automobile sealant, and uses thereof. [Means for solving the problem]

[0007] As a result of extensive research into the above-mentioned problems, the present inventors have discovered that a plastisol composition containing a vinyl chloride resin for paste processing having a specific degree of polymerization and vinyl acetate polymerization unit content, a plasticizer, and a diluent in specific blending amounts exhibits excellent processability and mechanical strength when processed at low temperatures (specifically, 80 to 100°C), and have completed the present invention.

[0008] That is, the present invention relates to a plastisol composition comprising at least a vinyl chloride-vinyl acetate copolymer for paste processing, a plasticizer, and a diluent, wherein the vinyl chloride-vinyl acetate copolymer for paste processing has 10 to 22% by weight of vinyl acetate polymerization units and an average degree of polymerization of 1000 to 3400, and the proportion of the vinyl chloride-vinyl acetate copolymer for paste processing to the total weight of the vinyl chloride-vinyl acetate copolymer for paste processing, the plasticizer, and the diluent is 40 to 58% by weight, and the proportion of the diluent to the total weight of the diluent and the plasticizer is 15 to 27% by weight, and to an automobile underbody coating agent and a sealant containing the plastisol composition.

[0009] The present invention will be described in detail below.

[0010] The plastisol composition of the present invention contains a vinyl chloride-vinyl acetate copolymer for paste processing having 10 to 22 wt% vinyl acetate polymerization units and an average degree of polymerization of 1,000 to 3,400. The vinyl chloride-vinyl acetate copolymer for paste processing has a vinyl acetate polymerization unit content of 10 to 22 wt% (i.e., the vinyl acetate polymerization unit content corresponds to 10 to 22 parts by weight per 100 parts by weight of the vinyl chloride-vinyl acetate copolymer for paste processing). This vinyl acetate polymerization unit content is excellent, particularly in low-temperature processing, and provides excellent mechanical strength and elongation, particularly for use in automotive underbody coats and automotive sealants, as well as excellent strength properties. Therefore, the vinyl acetate polymerization unit content is preferably 13 to 20 wt%, and more preferably 14 to 18 wt%. Here, a vinyl acetate polymerization unit content of less than 10 wt% is undesirable because molded articles obtained by low-temperature processing of the plastisol composition have low mechanical strength. On the other hand, an average vinyl acetate polymerization unit content of more than 22 wt% is undesirable because the viscosity of the sol changes significantly over time.

[0011] The average degree of polymerization of the vinyl chloride-vinyl acetate copolymer for paste processing can be determined, for example, by a method conforming to JIS-K6721, and is 1000 to 3400. Since the copolymer is particularly excellent for use in automobile underbody coats and automobile sealants, the average degree of polymerization is preferably 1400 to 2800, and more preferably 1800 to 2600. An average degree of polymerization less than 1000 is undesirable because the viscosity of the resulting sol changes significantly over time. On the other hand, an average degree of polymerization greater than 3400 requires a longer polymerization time during production, resulting in poor productivity.

[0012] The plastisol composition of the present invention exhibits excellent mechanical properties, particularly in low-temperature processing, and is particularly suitable for use as an automobile underbody coat or sealant. Therefore, it is preferable that the tensile strength be 0.1 MPa or more. For example, the plastisol composition is applied to a thickness of 2 mm, and heated at 80°C for 30 minutes to form a sheet. JIS No. 3 dumbbell test pieces are then prepared from the sheet, and the tensile strength is determined by measuring the tensile strength at 23°C and 50 mm / min in accordance with JIS K6251. It is also preferable that the elongation at this time be 35% or more.

[0013] The vinyl chloride-vinyl acetate copolymer for paste processing constituting the plastisol composition of the present invention may be any known vinyl chloride-vinyl acetate copolymer for paste processing that is generally suitable for paste processing, and for example, any vinyl chloride-vinyl acetate copolymer for paste processing obtained by polymerizing vinyl chloride monomer and vinyl acetate monomer by emulsion polymerization, microsuspension polymerization, seed emulsion polymerization, seed microsuspension polymerization, etc. may be used. Also, commercially available products may be used.

[0014] The plastisol composition of the present invention exhibits excellent processability and mechanical strength even when processed at low temperatures of 80 to 100°C, making it particularly suitable for use as a coating agent, especially for automobile underbody coatings and automobile sealants. Therefore, the blending ratio of the vinyl chloride-vinyl acetate copolymer for paste processing, plasticizer, and diluent constituting the plastisol composition is 40 to 58 wt%, preferably 45 to 55 wt%, based on the total weight of these components. Here, if the proportion of the vinyl chloride-vinyl acetate copolymer for paste processing is less than 40 wt%, the molded product obtained by low-temperature processing of the plastisol composition will have low mechanical strength, which is undesirable. On the other hand, if the proportion exceeds 58 wt%, the molded product obtained by low-temperature processing of the plastisol composition will have low elongation, which is undesirable. Furthermore, the proportion of the diluent relative to the total weight of the plasticizer and diluent is 15 to 27 wt%, preferably 17 to 25 wt%. Here, if the diluent content is less than 15% by weight, the viscosity of the sol will change significantly over time, which is undesirable, whereas if the diluent content exceeds 27% by weight, the molded product will have a low elongation when the plastisol composition is subjected to low-temperature processing, which is undesirable.

[0015] The plasticizer used in this case may be any plasticizer that belongs to the category of plasticizers that constitute plastisol compositions made of vinyl chloride resins for paste processing, and for example, bis(2-ethylhexyl) terephthalate (Hansen solubility parameter 17.9 (J / cm 3 ) 1 / 2 ), diisononyl phthalate (Hansen solubility parameter 17.6 (J / cm 3 ) 1 / 2 ), bis(2-ethylhexyl) phthalate (Hansen solubility parameter 17.6 (J / cm 3 ) 1 / 2 ), phthalate esters such as diethylene glycol dibenzoate (Hansen solubility parameter 19.9 (J / cm 3 ) 1 / 2aromatic carboxylic acid ester plasticizers such as alkylsulfonic acid phenyl esters; aromatic sulfonic acid ester plasticizers such as alkylsulfonic acid phenyl esters; bis(2-ethylhexyl) adipate (Hansen solubility parameter 16.6 (J / cm 3 ) 1 / 2 ), diisononyl adipate (Hansen solubility parameter 16.0 (J / cm 3 ) 1 / 2 ), dibutyl sebacate (Hansen solubility parameter 17.0 (J / cm 3 ) 1 / 2 ) and other sebacic acid esters, o-acetyl tributyl citrate (Hansen solubility parameter 17.7 (J / cm 3 ) 1 / 2 aliphatic ester plasticizers such as citrate esters; adipic acid polyester (Hansen solubility parameter 20.7 (J / cm 3 ) 1 / 2 Among these, polyesters with a Hansen solubility parameter (SP value) of 16.5 to 22.0 (J / cm) are particularly preferred, as they are excellent in low-temperature processability and mechanical strength and are suitable for use in automobile underbody coatings and automobile sealants. 3 ) 1 / 2 The Hansen solubility parameter can be calculated, for example, by computer software (trade name) HSPiP (Hansen Solubility Parameter in Practice).

[0016] Examples of diluents include normal paraffin hydrocarbon solvents, isoparaffin hydrocarbon solvents, naphthenic hydrocarbon solvents, and aromatic hydrocarbon solvents, and examples of commercially available diluents include Exxsol D80 (trade name, manufactured by TonenGeneral Sekiyu K.K.).

[0017] The plastisol composition of the present invention may contain additives that are usually added to plastisol compositions made from vinyl chloride resins for paste processing, such as fillers, stabilizers, antioxidants, flame retardants, lubricants, ultraviolet absorbers, colorants such as pigments, surfactants, antistatic agents, etc., within the range that does not exceed the object of the present invention, and the amounts of these additives may be within the ranges that are generally used.

[0018] The plastisol composition of the present invention has excellent processability and mechanical properties even under processing conditions as low as 80 to 100°C, and is suitable for a variety of applications such as films, sheets, wallpaper, flooring materials, and foam sheets, particularly as coating agents, and further as automotive underbody coating agents and automotive sealants. [Effects of the Invention]

[0019] The plastisol composition of the present invention has excellent mechanical properties when processed at low temperatures (specifically, 80 to 100° C.), and has excellent properties as a coating agent, particularly for automobile underbody coatings and automobile sealants. [Example]

[0020] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0021] The vinyl chloride-vinyl acetate copolymer for paste processing and the plastisol compositions obtained in the examples were evaluated as follows.

[0022] <Method for measuring tensile strength and elongation> The kneaded and degassed plastisol composition was applied to a thickness of 2 mm using release paper and heated at 80°C for 30 minutes to prepare a paste PVC sheet. Test pieces were prepared from the obtained paste PVC sheet using a JIS No. 3 dumbbell, and benchmark lines were marked at 20 mm intervals in the center of the test piece. The test piece was pulled at 23°C at a rate of 50 mm / min in accordance with JIS K6251, and the load at break and the elongation between the benchmark lines were measured to determine the breaking strength and breaking elongation.

[0023] <Measurement of average degree of polymerization> The average degree of polymerization of the vinyl chloride-vinyl acetate copolymer for paste processing was determined in accordance with JIS-K6721.

[0024] <Method for measuring vinyl acetate polymerization unit content> The vinyl acetate polymerization unit content (wt%) (sometimes referred to as VAc content) in the vinyl chloride-vinyl acetate copolymer for paste processing was calculated from the following formula using a measurement sample prepared by mixing 100 mg of vinyl chloride-vinyl acetate copolymer for paste processing with 10 mg of potassium bromide, grinding and molding the mixture, and an infrared spectrophotometer (Shimadzu Corporation, product name FTIR-8100A). VAc content=(3.73×B / A+0.024)×1.04 A:1430cm -1 Abs. value of the absorption peak top due to the CH in-plane bending angle near B:1740cm -1 Abs. value of the absorption peak top due to C=O stretching near

[0025] <Calculation method for plasticizer SP value> The Hansen solubility parameter (SP value) is the value expressed by δ using the following formula (unit: (J / cm 3 ) 1 / 2 ) δ=(δd 2 +δp 2 +δh 2 ) 1 / 2 Here, δd represents the dispersion term, δp represents the polar term, and δh represents the hydrogen bond term (all in units of (J / cm 3 ) 1 / 2 ). The δ, δd, δp, and δh of each plasticizer were calculated using commercially available computer software (product name) HSPiP (Hansen Solubility Parameter in Practice).

[0026] Synthesis Example 1 (Synthesis example of seed containing initiator, etc.) 1m 3An autoclave was charged with 360 kg of deionized water, 300 kg of vinyl chloride monomer, 6 kg of lauroyl peroxide, and 30 kg of a 15 wt% aqueous solution of sodium dodecylbenzenesulfonate. The polymerization solution was circulated using a homogenizer for 2 hours. After homogenization, the temperature was raised to 45°C and polymerization was allowed to proceed. After the pressure had dropped by 0.2 MPa below the saturated vapor pressure of vinyl chloride monomer at 45°C, unreacted vinyl chloride monomer was recovered. The resulting initiator-containing seed latex (hereinafter referred to as Seed 1) had an average particle size of 0.60 μm and a solids concentration of 32%.

[0027] Example 1 A 2.5-liter autoclave was charged with 500 g of deionized water, 473 g of vinyl chloride monomer, 124 g of vinyl acetate monomer, 8.6 g of 5 wt.% aqueous sodium lauryl sulfate, 81 g of seed 1, and 4 g of 0.1 wt.% aqueous copper sulfate solution. The temperature of the reaction mixture was then raised to 35°C to initiate the first-stage polymerization. A 0.06 wt.% aqueous ascorbic acid solution was added continuously throughout the entire polymerization to maintain the polymerization temperature. A total of 220 g of the 0.06 wt.% aqueous ascorbic acid solution was added throughout the entire polymerization. When the polymerization conversion rate reached 50%, 135 g of vinyl chloride monomer was charged to the 2.5-liter autoclave as the second-stage monomer, and the second-stage polymerization was continued at 35°C. Furthermore, when the polymerization conversion rate relative to the total of the first-stage and second-stage monomers was 80%, 68 g of vinyl chloride monomer was charged into a 2.5-liter autoclave as the third-stage monomer, and the third-stage polymerization was continued at a polymerization temperature of 35°C. The polymerization was terminated when the polymerization conversion rate relative to the total of the mixed monomers was 89%. From the start of polymerization to the end of polymerization, 120 g of a 5 wt% aqueous solution of sodium lauryl sulfate was continuously added. The total polymerization time from the start of polymerization to the end of polymerization was 782 minutes.

[0028] The unreacted monomer was then recovered to form a latex, which was then spray-dried in a spray dryer at a hot air inlet temperature of 158°C and an outlet temperature of 55°C to obtain a vinyl chloride-vinyl acetate copolymer for paste processing. The obtained vinyl chloride-vinyl acetate copolymer for paste processing had an average degree of polymerization of 1662 and a vinyl acetate polymer unit content of 11.7% by weight.

[0029] For 100 parts by weight of the obtained vinyl chloride-vinyl acetate copolymer for paste processing, diisononyl phthalate (product name DINP, manufactured by J-Plus Co., Ltd.; Hansen solubility parameter 17.6 (J / cm)) was used as a plasticizer. 3 ) 1 / 2 ) as a thixotropic agent, 70 parts by weight of fatty acid-treated calcium carbonate (trade name SP-60, manufactured by Takehara Chemical Industry Co., Ltd.) as a filler, 70 parts by weight of heavy calcium carbonate (trade name NN500, manufactured by Sankyo Seifun Co., Ltd.) as a filler, and 20 parts by weight of naphthenic hydrocarbon solvent (trade name Exxsol D80, manufactured by TonenGeneral Sekiyu K.K.) as a diluent were blended, and the mixture was kneaded and defoamed using a dissolver at 23°C for 3 minutes to obtain a plastisol composition.

[0030] Furthermore, a paste vinyl chloride sheet was produced using the obtained plastisol composition, and the physical properties were evaluated. The results are shown in Table 1.

[0031] Example 2 A 2.5-liter autoclave was charged with 500 g of deionized water, 393 g of vinyl chloride monomer, 239 g of vinyl acetate monomer, 8.6 g of 5 wt.% aqueous sodium lauryl sulfate solution, 81 g of seed 1, and 4 g of 0.1 wt.% aqueous copper sulfate solution as the first-stage monomer feed. The temperature of the reaction mixture was then raised to 35°C to initiate the first-stage polymerization, and a 0.06 wt.% aqueous ascorbic acid solution was continuously added throughout the entire polymerization to maintain the polymerization temperature. The total amount of 0.06 wt.% aqueous ascorbic acid added throughout the entire polymerization was 240 g. When the polymerization conversion rate reached 50%, 112 g of vinyl chloride monomer was charged to the 2.5-liter autoclave as the second-stage monomer feed, and the second-stage polymerization was continued at 35°C. Furthermore, when the polymerization conversion rate relative to the total of the first-stage and second-stage monomers was 80%, 56 g of vinyl chloride monomer was charged into a 2.5-liter autoclave as the third-stage monomer, and the third-stage polymerization was continued at a polymerization temperature of 35°C. The polymerization was terminated when the polymerization conversion rate relative to the total of the mixed monomers was 89%. From the start of polymerization to the end of polymerization, 120 g of a 5 wt% aqueous solution of sodium lauryl sulfate was continuously added. The total polymerization time from the start of polymerization to the end of polymerization was 1,059 minutes.

[0032] The unreacted monomer was then recovered to form a latex, which was then spray-dried in a spray dryer at a hot air inlet temperature of 158°C and an outlet temperature of 55°C to obtain a vinyl chloride-vinyl acetate copolymer for paste processing.

[0033] The obtained vinyl chloride-vinyl acetate copolymer for paste processing was a vinyl chloride-vinyl acetate copolymer having an average degree of polymerization of 1327 and a vinyl acetate polymer unit content of 21.1% by weight.

[0034] A plastisol composition was obtained, a paste vinyl chloride sheet was produced, and its physical properties were evaluated in the same manner as in Example 1, except that the obtained vinyl chloride-vinyl acetate copolymer for paste processing was used. The results are shown in Table 1.

[0035] Example 3 A 2.5-liter autoclave was charged with 500 g of deionized water, 449 g of vinyl chloride monomer, 159 g of vinyl acetate monomer, 8.6 g of 5 wt.% aqueous sodium lauryl sulfate solution, 81 g of seed 1, and 4 g of 0.1 wt.% aqueous copper sulfate solution as the first-stage monomer feed. The temperature of the reaction mixture was then raised to 40°C to initiate the first-stage polymerization, and a 0.06 wt.% aqueous ascorbic acid solution was continuously added throughout the entire polymerization to maintain the polymerization temperature. The total amount of 0.06 wt.% aqueous ascorbic acid added throughout the entire polymerization was 200 g. When the polymerization conversion rate reached 50%, 128 g of vinyl chloride monomer was charged to the 2.5-liter autoclave as the second-stage monomer feed, and the second-stage polymerization was continued at 40°C. Furthermore, when the polymerization conversion rate relative to the total of the first-stage and second-stage monomers was 80%, 64 g of vinyl chloride monomer was charged into a 2.5-liter autoclave as the third-stage monomer, and the third-stage polymerization was continued at a polymerization temperature of 40°C. The polymerization was terminated when the polymerization conversion rate relative to the total of the mixed monomers was 89%. From the start of polymerization to the end of polymerization, 120 g of a 5 wt% aqueous solution of sodium lauryl sulfate was continuously added. The total polymerization time from the start of polymerization to the end of polymerization was 644 minutes.

[0036] The unreacted monomer was then recovered to form a latex, which was then spray-dried in a spray dryer at a hot air inlet temperature of 158°C and an outlet temperature of 55°C to obtain a vinyl chloride-vinyl acetate copolymer for paste processing.

[0037] The obtained vinyl chloride-vinyl acetate copolymer for paste processing was a vinyl chloride-vinyl acetate copolymer having an average degree of polymerization of 1227 and a vinyl acetate polymer unit content of 15.0% by weight.

[0038] A plastisol composition was obtained, a paste vinyl chloride sheet was produced, and its physical properties were evaluated in the same manner as in Example 1, except that the obtained vinyl chloride-vinyl acetate copolymer for paste processing was used. The results are shown in Table 1.

[0039] Example 4 A 2.5-liter autoclave was charged with 500 g of deionized water, 449 g of vinyl chloride monomer, 159 g of vinyl acetate monomer, 8.6 g of 5 wt.% aqueous sodium lauryl sulfate solution, 81 g of seed 1, and 4 g of 0.1 wt.% aqueous copper sulfate solution as the first-stage monomer feed. The temperature of the reaction mixture was then raised to 20°C to initiate the first-stage polymerization, and 0.1 wt.% aqueous ascorbic acid solution was continuously added throughout the entire polymerization to maintain the polymerization temperature. The total amount of 0.1 wt.% aqueous ascorbic acid added throughout the entire polymerization was 450 g. When the polymerization conversion rate reached 50%, 128 g of vinyl chloride monomer was charged to the 2.5-liter autoclave as the second-stage monomer feed, and the second-stage polymerization was continued at 20°C. Furthermore, when the polymerization conversion rate relative to the total of the first-stage and second-stage monomers was 80%, 64 g of vinyl chloride monomer was charged into a 2.5-liter autoclave as the third-stage monomer, and the third-stage polymerization was continued at a polymerization temperature of 20°C. The polymerization was terminated when the polymerization conversion rate relative to the total of the mixed monomers was 89%. From the start of polymerization to the end of polymerization, 120 g of a 5 wt% aqueous solution of sodium lauryl sulfate was continuously added. The total polymerization time from the start of polymerization to the end of polymerization was 1,740 minutes.

[0040] The unreacted monomer was then recovered to form a latex, which was then spray-dried in a spray dryer at a hot air inlet temperature of 158°C and an outlet temperature of 55°C to obtain a vinyl chloride-vinyl acetate copolymer for paste processing. The obtained vinyl chloride-vinyl acetate copolymer for paste processing had an average degree of polymerization of 3348 and a vinyl acetate polymer unit content of 14.6% by weight.

[0041] A plastisol composition was obtained, a paste vinyl chloride sheet was produced, and its physical properties were evaluated in the same manner as in Example 1, except that the obtained vinyl chloride-vinyl acetate copolymer for paste processing was used. The results are shown in Table 1.

[0042] Example 5 A 2.5-liter autoclave was charged with 500 g of deionized water, 449 g of vinyl chloride monomer, 159 g of vinyl acetate monomer, 8.6 g of 5 wt.% sodium lauryl sulfate aqueous solution, 81 g of seed 1, and 4 g of 0.1 wt.% copper sulfate aqueous solution as the first-stage monomer feed. The temperature of the reaction mixture was then raised to 35°C to initiate the first-stage polymerization, and a 0.06 wt.% ascorbic acid aqueous solution was continuously added throughout the entire polymerization to maintain the polymerization temperature. The total amount of 0.06 wt.% ascorbic acid aqueous solution added throughout the entire polymerization was 210 g. When the polymerization conversion rate reached 50%, 128 g of vinyl chloride monomer was charged to the 2.5-liter autoclave as the second-stage monomer feed, and the second-stage polymerization was continued at a polymerization temperature of 35°C. Furthermore, when the polymerization conversion rate relative to the total of the first-stage and second-stage monomers was 80%, 64 g of vinyl chloride monomer was charged into a 2.5-liter autoclave as the third-stage monomer, and the third-stage polymerization was continued at a polymerization temperature of 35°C. The polymerization was terminated when the polymerization conversion rate relative to the total of the mixed monomers was 89%. From the start of polymerization to the end of polymerization, 120 g of a 5 wt% aqueous solution of sodium lauryl sulfate was continuously added. The total polymerization time from the start of polymerization to the end of polymerization was 758 minutes.

[0043] The unreacted monomer was then recovered to form a latex, which was then spray-dried in a spray dryer at a hot air inlet temperature of 158°C and an outlet temperature of 55°C to obtain a vinyl chloride-vinyl acetate copolymer for paste processing.

[0044] The obtained vinyl chloride-vinyl acetate copolymer for paste processing was a vinyl chloride-vinyl acetate copolymer having an average degree of polymerization of 1552 and a vinyl acetate polymer unit content of 13.9% by weight.

[0045] A plastisol composition was obtained using the vinyl chloride-vinyl acetate copolymer for paste processing obtained above, and a paste vinyl chloride sheet was prepared and its physical properties were evaluated in the same manner as in Example 1, except that the formulation was as shown in Table 1. The results are shown in Table 1.

[0046] Example 6 A 2.5-liter autoclave was charged with 500 g of deionized water, 449 g of vinyl chloride monomer, 159 g of vinyl acetate monomer, 8.6 g of 5 wt.% sodium lauryl sulfate aqueous solution, 81 g of seed 1, and 4 g of 0.1 wt.% copper sulfate aqueous solution as the first-stage monomer feed. The temperature of the reaction mixture was then raised to 35°C to initiate the first-stage polymerization, and a 0.06 wt.% ascorbic acid aqueous solution was continuously added throughout the entire polymerization to maintain the polymerization temperature. The total amount of 0.06 wt.% ascorbic acid aqueous solution added throughout the entire polymerization was 210 g. When the polymerization conversion rate reached 50%, 128 g of vinyl chloride monomer was charged to the 2.5-liter autoclave as the second-stage monomer feed, and the second-stage polymerization was continued at a polymerization temperature of 35°C. Furthermore, when the polymerization conversion rate relative to the total of the first-stage and second-stage monomers was 80%, 64 g of vinyl chloride monomer was charged into a 2.5-liter autoclave as the third-stage monomer, and the third-stage polymerization was continued at a polymerization temperature of 35°C. The polymerization was terminated when the polymerization conversion rate relative to the total of the mixed monomers was 89%. From the start of polymerization to the end of polymerization, 120 g of a 5 wt% aqueous solution of sodium lauryl sulfate was continuously added. The total polymerization time from the start of polymerization to the end of polymerization was 758 minutes.

[0047] The unreacted monomer was then recovered to form a latex, which was then spray-dried in a spray dryer at a hot air inlet temperature of 158°C and an outlet temperature of 55°C to obtain a vinyl chloride-vinyl acetate copolymer for paste processing.

[0048] The obtained vinyl chloride-vinyl acetate copolymer for paste processing was a vinyl chloride-vinyl acetate copolymer having an average degree of polymerization of 1552 and a vinyl acetate residue unit content of 13.9% by weight.

[0049] A plastisol composition was obtained using the vinyl chloride-vinyl acetate copolymer for paste processing obtained above, and a paste vinyl chloride sheet was prepared and its physical properties were evaluated in the same manner as in Example 1, except that the formulation was as shown in Table 1. The results are shown in Table 1.

[0050] Example 7 A 2.5-liter autoclave was charged with 500 g of deionized water, 449 g of vinyl chloride monomer, 159 g of vinyl acetate monomer, 8.6 g of 5 wt.% aqueous sodium lauryl sulfate solution, 81 g of seed 1, and 4 g of 0.1 wt.% aqueous copper sulfate solution as the first-stage monomer feed. The temperature of the reaction mixture was then raised to 25°C to initiate the first-stage polymerization, and a 0.06 wt.% aqueous ascorbic acid solution was continuously added throughout the entire polymerization to maintain the polymerization temperature. The total amount of 0.06 wt.% aqueous ascorbic acid added throughout the entire polymerization was 340 g. When the polymerization conversion rate reached 50%, 128 g of vinyl chloride monomer was charged to the 2.5-liter autoclave as the second-stage monomer feed, and the second-stage polymerization was continued at 25°C. Furthermore, when the polymerization conversion rate relative to the total of the first-stage and second-stage monomers was 80%, 64 g of vinyl chloride monomer was charged into a 2.5-liter autoclave as the third-stage monomer, and the third-stage polymerization was continued at a polymerization temperature of 25°C. The polymerization was terminated when the polymerization conversion rate relative to the total of the mixed monomers was 89%. From the start of polymerization to the end of polymerization, 120 g of a 5 wt% aqueous solution of sodium lauryl sulfate was continuously added. The total polymerization time from the start of polymerization to the end of polymerization was 1,560 minutes.

[0051] The unreacted monomer was then recovered to form a latex, which was then spray-dried in a spray dryer at a hot air inlet temperature of 158°C and an outlet temperature of 55°C to obtain a vinyl chloride-vinyl acetate copolymer for paste processing.

[0052] The obtained vinyl chloride-vinyl acetate copolymer for paste processing was a vinyl chloride-vinyl acetate copolymer having an average degree of polymerization of 2621 and a vinyl acetate residue unit content of 14.6% by weight.

[0053] A plastisol composition was obtained using the vinyl chloride-vinyl acetate copolymer for paste processing obtained above, and a paste vinyl chloride sheet was prepared and its physical properties were evaluated in the same manner as in Example 1, except that the formulation was as shown in Table 1. The results are shown in Table 1.

[0054] Example 8 A 2.5-liter autoclave was charged with 500 g of deionized water, 449 g of vinyl chloride monomer, 159 g of vinyl acetate monomer, 8.6 g of 5 wt.% sodium lauryl sulfate aqueous solution, 81 g of seed 1, and 4 g of 0.1 wt.% copper sulfate aqueous solution as the first-stage monomer feed. The temperature of the reaction mixture was then raised to 35°C to initiate the first-stage polymerization, and a 0.06 wt.% ascorbic acid aqueous solution was continuously added throughout the entire polymerization to maintain the polymerization temperature. The total amount of 0.06 wt.% ascorbic acid aqueous solution added throughout the entire polymerization was 210 g. When the polymerization conversion rate reached 50%, 128 g of vinyl chloride monomer was charged to the 2.5-liter autoclave as the second-stage monomer feed, and the second-stage polymerization was continued at a polymerization temperature of 35°C. Furthermore, when the polymerization conversion rate relative to the total of the first-stage and second-stage monomers was 80%, 64 g of vinyl chloride monomer was charged into a 2.5-liter autoclave as the third-stage monomer, and the third-stage polymerization was continued at a polymerization temperature of 35°C. The polymerization was terminated when the polymerization conversion rate relative to the total of the mixed monomers was 89%. From the start of polymerization to the end of polymerization, 120 g of a 5 wt% aqueous solution of sodium lauryl sulfate was continuously added. The total polymerization time from the start of polymerization to the end of polymerization was 758 minutes.

[0055] The unreacted monomer was then recovered to form a latex, which was then spray-dried in a spray dryer at a hot air inlet temperature of 158°C and an outlet temperature of 55°C to obtain a vinyl chloride-vinyl acetate copolymer for paste processing.

[0056] The obtained vinyl chloride resin for paste processing was a vinyl chloride-vinyl acetate copolymer having an average degree of polymerization of 1552 and an average vinyl acetate residue unit content of 13.9% by weight.

[0057] The obtained vinyl chloride-vinyl acetate copolymer for paste processing was treated with dibutyl sebacate (trade name DBS, Fujifilm Wako Pure Chemical Industries, Ltd.) instead of diisononyl phthalate as a plasticizer; the Hansen solubility parameter was 17.0 (J / cm 3 ) 1 / 2A plastisol composition was obtained, a paste vinyl chloride sheet was produced, and the physical properties were evaluated in the same manner as in Example 1, except that the formulation shown in Table 1 was used. The results are shown in Table 1.

[0058] Example 9 A 2.5-liter autoclave was charged with 500 g of deionized water, 449 g of vinyl chloride monomer, 159 g of vinyl acetate monomer, 8.6 g of 5 wt.% sodium lauryl sulfate aqueous solution, 81 g of seed 1, and 4 g of 0.1 wt.% copper sulfate aqueous solution as the first-stage monomer feed. The temperature of the reaction mixture was then raised to 35°C to initiate the first-stage polymerization, and a 0.06 wt.% ascorbic acid aqueous solution was continuously added throughout the entire polymerization to maintain the polymerization temperature. The total amount of 0.06 wt.% ascorbic acid aqueous solution added throughout the entire polymerization was 210 g. When the polymerization conversion rate reached 50%, 128 g of vinyl chloride monomer was charged to the 2.5-liter autoclave as the second-stage monomer feed, and the second-stage polymerization was continued at a polymerization temperature of 35°C. Furthermore, when the polymerization conversion rate relative to the total of the first-stage and second-stage monomers was 80%, 64 g of vinyl chloride monomer was charged into a 2.5-liter autoclave as the third-stage monomer, and the third-stage polymerization was continued at a polymerization temperature of 35°C. The polymerization was terminated when the polymerization conversion rate relative to the total of the mixed monomers was 89%. From the start of polymerization to the end of polymerization, 120 g of a 5 wt% aqueous solution of sodium lauryl sulfate was continuously added. The total polymerization time from the start of polymerization to the end of polymerization was 758 minutes.

[0059] The unreacted monomer was then recovered to form a latex, which was then spray-dried in a spray dryer at a hot air inlet temperature of 158°C and an outlet temperature of 55°C to obtain a vinyl chloride-vinyl acetate copolymer for paste processing.

[0060] The obtained vinyl chloride-vinyl acetate copolymer for paste processing was a vinyl chloride-vinyl acetate copolymer having an average degree of polymerization of 1552 and a vinyl acetate residue unit content of 13.9% by weight.

[0061] The obtained vinyl chloride-vinyl acetate copolymer for paste processing was plasticized with adipic acid polyester (product name D620, manufactured by J-Plus Co., Ltd.) instead of diisononyl phthalate; the Hansen solubility parameter was 20.7 (J / cm). 3 ) 1 / 2 A plastisol composition was obtained, a paste vinyl chloride sheet was produced, and the physical properties were evaluated in the same manner as in Example 1, except that the formulation shown in Table 1 was used. The results are shown in Table 1.

[0062] [Table 1]

[0063] Comparative Example 1 A 2.5-liter autoclave was charged with 500 g of deionized water, 484 g of vinyl chloride monomer, 108 g of vinyl acetate monomer, 8.6 g of 5 wt.% sodium lauryl sulfate aqueous solution, 81 g of seed 1, and 4 g of 0.1 wt.% copper sulfate aqueous solution as the first-stage monomer feed. The temperature of the reaction mixture was then raised to 35°C to initiate the first-stage polymerization, and a 0.06 wt.% ascorbic acid aqueous solution was continuously added throughout the entire polymerization to maintain the polymerization temperature. The total amount of 0.06 wt.% ascorbic acid aqueous solution added throughout the entire polymerization was 220 g. When the polymerization conversion rate reached 50%, 138 g of vinyl chloride monomer was charged to the 2.5-liter autoclave as the second-stage monomer feed, and the second-stage polymerization was continued at a polymerization temperature of 35°C. Furthermore, when the polymerization conversion rate relative to the total of the first-stage and second-stage monomers was 80%, 69 g of vinyl chloride monomer was charged into a 2.5-liter autoclave as the third-stage monomer, and the third-stage polymerization was continued at a polymerization temperature of 35°C. The polymerization was terminated when the polymerization conversion rate relative to the total of the mixed monomers was 89%. From the start of polymerization to the end of polymerization, 120 g of a 5 wt% aqueous solution of sodium lauryl sulfate was continuously added. The total polymerization time from the start of polymerization to the end of polymerization was 792 minutes.

[0064] The unreacted monomer was then recovered to form a latex, which was then spray-dried in a spray dryer at a hot air inlet temperature of 158°C and an outlet temperature of 55°C to obtain a vinyl chloride resin for paste processing.

[0065] The obtained vinyl chloride resin for paste processing was a vinyl chloride-vinyl acetate copolymer having an average degree of polymerization of 1897 and a vinyl acetate polymer unit content of 9.0% by weight.

[0066] A plastisol composition was obtained using the vinyl chloride-vinyl acetate copolymer for paste processing obtained above, and a paste PVC sheet was prepared and its physical properties were evaluated in the same manner as in Example 1, except that the formulation shown in Table 2 was used. The results are shown in Table 2. The tensile strength of the paste PVC sheet when processed at 80°C was 0.07 MPa, which was low.

[0067] Comparative Example 2 A 2.5-liter autoclave was charged with 500 g of deionized water, 449 g of vinyl chloride monomer, 159 g of vinyl acetate monomer, 8.6 g of 5 wt.% sodium lauryl sulfate aqueous solution, 81 g of seed 1, and 4 g of 0.1 wt.% copper sulfate aqueous solution as the first-stage monomer feed. The temperature of the reaction mixture was then raised to 35°C to initiate the first-stage polymerization, and a 0.06 wt.% ascorbic acid aqueous solution was continuously added throughout the entire polymerization to maintain the polymerization temperature. The total amount of 0.06 wt.% ascorbic acid aqueous solution added throughout the entire polymerization was 210 g. When the polymerization conversion rate reached 50%, 128 g of vinyl chloride monomer was charged to the 2.5-liter autoclave as the second-stage monomer feed, and the second-stage polymerization was continued at a polymerization temperature of 35°C. Furthermore, when the polymerization conversion rate relative to the total of the first-stage and second-stage monomers was 80%, 64 g of vinyl chloride monomer was charged into a 2.5-liter autoclave as the third-stage monomer, and the third-stage polymerization was continued at a polymerization temperature of 35°C. The polymerization was terminated when the polymerization conversion rate relative to the total of the mixed monomers was 89%. From the start of polymerization to the end of polymerization, 120 g of a 5 wt% aqueous solution of sodium lauryl sulfate was continuously added. The total polymerization time from the start of polymerization to the end of polymerization was 758 minutes.

[0068] The unreacted monomer was then recovered to form a latex, which was then spray-dried in a spray dryer at a hot air inlet temperature of 158°C and an outlet temperature of 55°C to obtain a vinyl chloride resin for paste processing.

[0069] The obtained vinyl chloride resin for paste processing was a vinyl chloride-vinyl acetate copolymer having an average degree of polymerization of 1552 and a vinyl acetate polymer unit content of 13.9% by weight.

[0070] A plastisol composition was obtained in the same manner as in Example 1, except that the obtained vinyl chloride-vinyl acetate copolymer for paste processing was used and the formulation shown in Table 2 was used. The composition was applied to a thickness of 2 mm using release paper and heated at 80°C for 30 minutes to attempt to produce a sheet, but the composition did not harden.

[0071] Comparative Example 3 A 2.5-liter autoclave was charged with 500 g of deionized water, 449 g of vinyl chloride monomer, 159 g of vinyl acetate monomer, 8.6 g of 5 wt.% sodium lauryl sulfate aqueous solution, 81 g of seed 1, and 4 g of 0.1 wt.% copper sulfate aqueous solution as the first-stage monomer feed. The temperature of the reaction mixture was then raised to 35°C to initiate the first-stage polymerization, and a 0.06 wt.% ascorbic acid aqueous solution was continuously added throughout the entire polymerization to maintain the polymerization temperature. The total amount of 0.06 wt.% ascorbic acid aqueous solution added throughout the entire polymerization was 210 g. When the polymerization conversion rate reached 50%, 128 g of vinyl chloride monomer was charged to the 2.5-liter autoclave as the second-stage monomer feed, and the second-stage polymerization was continued at a polymerization temperature of 35°C. Furthermore, when the polymerization conversion rate relative to the total of the first-stage and second-stage monomers was 80%, 64 g of vinyl chloride monomer was charged into a 2.5-liter autoclave as the third-stage monomer, and the third-stage polymerization was continued at a polymerization temperature of 35°C. The polymerization was terminated when the polymerization conversion rate relative to the total of the mixed monomers was 89%. From the start of polymerization to the end of polymerization, 120 g of a 5 wt% aqueous solution of sodium lauryl sulfate was continuously added. The total polymerization time from the start of polymerization to the end of polymerization was 758 minutes.

[0072] The unreacted monomer was then recovered to form a latex, which was then spray-dried in a spray dryer at a hot air inlet temperature of 158°C and an outlet temperature of 55°C to obtain a vinyl chloride resin for paste processing.

[0073] The obtained vinyl chloride resin for paste processing was a vinyl chloride-vinyl acetate copolymer having an average degree of polymerization of 1552 and a vinyl acetate polymer unit content of 13.9% by weight.

[0074] A plastisol composition was obtained using the vinyl chloride-vinyl acetate copolymer for paste processing obtained above, and a paste PVC sheet was prepared and its physical properties were evaluated in the same manner as in Example 1, except that the formulation shown in Table 2 was used. The results are shown in Table 2. The elongation of the paste PVC sheet when processed at 80°C was low, at 25%.

[0075] [Table 2] [Industrial Applicability]

[0076] The plastisol of the present invention has excellent processability and mechanical properties even when processed at low temperatures, for example, 80 to 100°C, and has excellent properties as a coating agent, particularly for automobile underbody coatings and automobile sealants, and is therefore highly useful industrially.

Claims

1. A plastisol composition comprising at least a vinyl chloride-vinyl acetate copolymer for paste processing, a plasticizer, and a diluent, wherein the vinyl chloride-vinyl acetate copolymer for paste processing is a vinyl chloride-vinyl acetate copolymer for paste processing having 10 to 22% by weight of vinyl acetate polymerization units and an average degree of polymerization of 1,000 to 3,400, and wherein the ratio of the vinyl chloride-vinyl acetate copolymer for paste processing to the total weight of the vinyl chloride-vinyl acetate copolymer for paste processing, the plasticizer, and the diluent satisfies the following conditions: 40 to 58% by weight, and the ratio of the diluent to the total weight of the diluent and the plasticizer is 15 to 27% by weight.

2. The plasticizer has a Hansen solubility parameter of 16.5 to 22.0 (J / cm ３ ) １／２ 2. The plastisol composition according to claim 1, wherein the plasticizer is selected from the group consisting of methyl methyl acrylate and methyl methacrylate.

3. The plastisol composition according to claim 1, characterized in that a 2 mm thick sheet is prepared under heating conditions of 80°C for 30 minutes, and a tensile test is carried out in accordance with JIS K6251 using a JIS No. 3 dumbbell test piece obtained from the sheet, and the tensile strength is 0.1 MPa or more and an elongation is 35% or more.

4. 10. A low-temperature processable automotive underbody coating agent comprising the plastisol composition of claim 1.

5. A sealant for low-temperature processing, comprising the plastisol composition according to claim 1.

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