JP2008239825A - Acrylic resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acrylic resin composition having sufficient strength, hardness and dimension stability and having excellent impact-resistance and chemical crack-resistance. <P>SOLUTION: The acrylic resin composition contains an acrylic resin, a granular additive having a modulus of elasticity being 15% or less of the acrylic resin, and a fiber. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an acrylic resin composition, and more particularly to an acrylic resin composition used for a structural material that requires chemical resistance.

  Acrylic resin, especially methacrylic resin (polymethyl methacrylate: PMMA) has the highest hardness among thermoplastic resins, and also has excellent chemical resistance against acids and alkalis, so it is widely used in various molded products. ing.

  However, since acrylic resin has a relatively low impact resistance and may have a sharp fracture surface when cracked, it must be used with care. Furthermore, the acrylic resin has a problem that when a solvent acts on a portion having a large residual strain, a chemical stress phenomenon is caused and so-called chemical cracks are easily generated.

In order to cope with such problems, conventionally, rubber particles such as acrylic rubber are blended with acrylic resin to increase the impact resistance of the acrylic resin, and the residual strain is reduced to improve the chemical crack resistance. (See Patent Document 1).
JP 04-164950 A

  However, in order to obtain the required impact resistance and chemical crack resistance, if a large amount of rubber particles such as acrylic rubber is blended in the acrylic resin, the strength and hardness are reduced compared to the case of the acrylic resin alone, and the temperature is reduced. There has been a problem that the dimensional stability due to the increase causes a decrease in dimensional stability.

  The present invention has been made in view of the circumstances as described above, and provides an acrylic resin composition having sufficient strength, hardness, and dimensional stability, as well as excellent impact resistance and chemical crack resistance. It is an issue.

  The present invention is characterized by the following in order to solve the above problems.

  1stly, the acrylic resin composition of this invention contains an acrylic resin, the granular additive whose elastic modulus is 15% or less of an acrylic resin, and a fiber, It is characterized by the above-mentioned.

  Second, in the first acrylic resin composition, the ratio of the average fiber length to the average particle diameter of the granular additive is in the range of 1/3 to 2.

  3rdly, in the said 1st or 2nd acrylic resin composition, content of a granular additive is 10 volume% or less with respect to the whole acrylic resin composition, and content of a fiber is with respect to a granular additive. The volume ratio is in the range of 1/3 to 2 times.

  Fourth, in any one of the first to third acrylic resin compositions, the average particle diameter of the granular additive is 25 μm or less.

  Fifth, in any one of the first to fourth acrylic resin compositions, the ratio of the average fiber diameter to the average length is 1/10 or less.

  Sixth, in any one of the first to fifth acrylic resin compositions, the particulate additive is a polytetrafluoroethylene resin.

  Seventh, the acrylic resin composition according to any one of the first to sixth aspects is characterized in that the acrylic resin is polymethyl methacrylate.

  According to the first to seventh inventions, the fiber is used in combination with the particulate additive having a specific elastic modulus. Therefore, when stress is applied to the molded article of the acrylic resin composition, a craze based on the particles is generated due to the stress concentration generated in the vicinity of the particles of the granular additive, but the fibers existing in the vicinity of the particles Effectively suppresses the development of crazes. Therefore, impact resistance and chemical crack resistance are improved without adding a large amount of particulate additive. Therefore, an acrylic resin composition having sufficient strength, hardness, and dimensional stability, and excellent impact resistance and chemical crack resistance is provided.

  The present invention has the features as described above, and an embodiment thereof will be described below.

  Examples of the acrylic resin used in the present invention include an acrylic ester polymer and a methacrylic ester polymer. Among them, it is preferable to use a methacrylic resin which is a polymer having a methyl methacrylate unit as a main component because of its high hardness and excellent chemical resistance to acids and alkalis.

  Specific examples of such a methacrylic resin include polymethyl methacrylate and copolymers of methyl methacrylate and other monomers.

  The copolymer of methyl methacrylate and other monomers preferably contains 80% by weight or more of methyl methacrylate units, and examples thereof include random copolymers. Specific examples of other monomers include methacrylic acid alkyl esters such as ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate; methyl acrylate, ethyl acrylate, butyl acrylate, acrylic acid 2 -Acrylic acid alkyl esters such as ethylhexyl; aromatic vinyl monomers such as styrene and α-methylstyrene. These monomers may be used individually by 1 type, and may be used in combination of 2 or more type. However, when 1,3-butadiene or the like, which is a rubber component, is copolymerized, there is a risk that the hardness may be lowered. Therefore, it is desirable to avoid use in the present invention.

  The weight average molecular weight of the methacrylic resin is appropriately determined in consideration of fluidity at the time of molding, chemical resistance, strength of the molded product, etc. For example, PMMA using GPC (gel permeation chromatography) is used. The value measured as a standard sample is in the range of 50,000 to 150,000.

  The methacrylic resin is produced by a known radical polymerization method such as bulk polymerization, solution polymerization, suspension polymerization, etc., using a radical polymerization initiator such as an organic peroxide or an azo compound, and a chain transfer agent such as mercaptan. Can do.

  The granular additive used in the present invention is a powder having an elastic modulus of 15% or less, preferably 0.01% to 15% of the acrylic resin.

  In the present invention, the “elastic modulus” is a tensile elastic modulus measured according to JIS K7127.

  By setting the elastic modulus of the granular additive to 15% or less of the acrylic resin, the impact resistance of the molded product can be improved. The lower limit of the elastic modulus of the particulate additive is not particularly limited, but if it is less than 0.01%, the particle becomes unstable and is not practical.

  The average particle size of the particulate additive is preferably 25 μm or less, more preferably in the range of 0.1 μm to 25 μm. Here, the average particle diameter is obtained by measuring the diameters of a considerable number of particles randomly selected from enlarged photographs or images obtained by a scanning electron microscope, and arithmetically averaging them. The granular additive used in the present invention is preferably spherical, but when the particles cannot be regarded as spherical, the major axis and minor axis were established, and the arithmetic average value was taken as the average diameter (particle diameter).

  By setting the average particle diameter of the granular additive to 25 μm or less, the impact resistance is improved by mixing and uniformly dispersing in the acrylic resin. However, if the average particle size is less than 0.1 μm, the impact resistance may not be sufficiently improved.

  Specific examples of the particulate additive include resin particle powder such as polytetrafluoroethylene (PTFE) resin, organic rubber particle powder, and the like. Here, the PTFE resin used as the particulate additive in the present invention is a particle substantially made of polytetrafluoroethylene. Polytetrafluoroethylene is typically a tetrafluoroethylene homopolymer, but in addition to this, a small amount of a modifier such as perfluoroolefin, hydrofluoroolefin, perfluorovinyl ether and the like are added together with tetrafluoroethylene as a monomer component. It may be copolymerized. As the PTFE resin, a baked one is typically used, and its melting point is, for example, 300 ° C. or higher.

  In particular, it is preferable to use a granular additive having a heat resistant temperature of 250 ° C. or higher. In the present invention, the “heat-resistant temperature” is a lower limit temperature (thermal decomposition temperature) that chemically denatures by a decomposition reaction or the like when continuously used at the temperature.

  By using a granular additive having a heat resistant temperature of 250 ° C. or higher, the granular additive is not denatured even at a high temperature during the preparation or molding of the acrylic resin composition, and the impact resistance and resistance of the molded product are improved. Chemical cracking properties can be improved.

  The ratio of the average diameter and the average length of the fibers used in the present invention is preferably 1/10 or less, more preferably 1/100 to 1/10. Here, the average diameter and the average length of the fibers are obtained by measuring the diameter or the total length of a considerable number of fibers randomly selected from an enlarged photograph or an image obtained by a scanning electron microscope and arithmetically averaging them.

  When the ratio of the average diameter and the average length of the fiber is 1/10 or less, when stress is applied to the molded product, the particle is generated based on the concentration of stress generated in the vicinity of the particles of the granular additive. Craze progress can be effectively suppressed. Thereby, impact resistance and chemical crack resistance are improved.

  The lower limit of the ratio between the average diameter and the average length of the fiber is not particularly limited, but if it is less than 1/100, the strength and stability of the fiber itself may be insufficient.

As such fibers, inorganic fibers and organic fibers can be used. Specific examples of the inorganic fiber include wollastonite, potassium titanate whisker, aluminum borate whisker, zonolite (6Ca · 6SiO ₂ · H ₂ O), sepiolite (magnesium silicate), elastadite (Ca ₁₀ ((SiO ₄ ) ₃ (SO ₄ ) ₃ ) (OH, Cl, F) _{2 and the} like.

  Specific examples of the organic fiber include carbon fiber, polyester fiber, imide fiber, aramid fiber, Kevlar (registered trademark), and the like.

  In the present invention, the ratio of the average fiber length to the average particle diameter of the particulate additive is preferably in the range of 1/3 to 2. By making the ratio within this range, when stress is applied to the molded product, the concentration of stress generated near the particles of the granular additive effectively suppresses the progress of the craze generated from the particles. Can do. Thereby, impact resistance and chemical crack resistance are improved. If the ratio is too small, it becomes difficult to suppress the progress of crazing. On the other hand, if the ratio is too large, the probability that fibers are present around the particles of the granular additive becomes small when the volume of the total amount of fibers is constant. Therefore, it becomes difficult to suppress the progress of craze, and the elastic modulus of the entire molded product may be increased to inhibit the effect of the present invention.

  Furthermore, in this invention, content of a granular additive is 10 volume% or less with respect to the whole acrylic resin composition, and content of a fiber exists in the range of 1 / 3-2 times by volume ratio with respect to a granular additive. It is preferable that it exists in. The content of the particulate additive is more preferably 5% by volume or less, still more preferably in the range of 0.2% by volume to 5% by volume with respect to the entire acrylic resin composition. More preferably, the fiber content is in the range of 1/3 to 1.5 times the volume of the particulate additive.

  By setting the content of the particulate additive and fiber within the above range, the acrylic resin composition has sufficient strength, hardness, and dimensional stability, and also has excellent impact resistance and chemical crack resistance. be able to. If the amount of the particulate additive is too large, the hardness is lowered, while if the amount of the particulate additive is too small, sufficient impact resistance cannot be obtained. Further, if the amount of fiber is excessive with respect to the particulate additive, sufficient impact resistance cannot be obtained. On the other hand, if the amount of fiber is too small relative to the particulate additive, the progress of craze cannot be sufficiently suppressed.

  The acrylic resin composition of the present invention includes various other additive components, for example, an ultraviolet absorber, a colorant, a heat stabilizer, an oxidation stabilizer, an antistatic agent and the like within a range not impeding the effects of the present invention. Can be blended.

  The acrylic resin composition of the present invention is prepared by heating and mixing the above-described particulate additive, fiber, and other additive components as necessary with a melted acrylic resin using a biaxial kneader, and cooling. The particulate additive and the fiber can be obtained in the form of pellets or the like as a uniform dispersion in the acrylic resin. The molding material of the acrylic resin composition thus obtained can be used for various molding methods such as injection molding and extrusion molding.

  The molded article by the acrylic resin composition of the present invention has sufficient strength, hardness, and dimensional stability, and has excellent impact resistance and chemical crack resistance. In particular, it can be suitably used as a structural material for applications requiring chemical resistance.

  Therefore, an example will be shown below and will be described in more detail. Of course, the invention is not limited by the following examples.

In the following Examples and Comparative Examples, the amount of each component represents parts by weight unless otherwise specified. Moreover, the evaluation test of the test molded article was performed under the following conditions.
(1) Charpy impact strength The Charpy impact strength of the test molded article was measured according to the method described in JIS K7171.
(2) Chemical crack resistance test The chemical crack resistance test was carried out by the following method. As shown in FIG. 1, a jig 2 having a convex curved surface 1 is used, and a test molded product A having a thickness of 3 mm and a width of 15 mm is placed on the jig 2 while being bent along the convex curved surface 1. The both ends of the test molded product A were fixed with the fasteners 3. Thus, by fixing the test molded product A on the convex curved surface 1 of the jig 2 in a bent state, 0.15%, 0.3%, 0.45% on the surface of the test molded product A is obtained. Four kinds of strains of 0.6% were applied. Here, by using four kinds of jigs 2 in which the curvature of the convex curved surface 1 is set so that the upper surface of the test molded product A is stretched in the range of 0.15 to 0.6%, this 4 is used. Added some kind of distortion.

Next, the cylinder 4 having an inner diameter of 5 mm with the top and bottom opened was fixed to the upper surface of the central portion of the test molded article A with silicon grease, and the cylinder 4 was filled with ethyl alcohol and left for 24 hours. The strain when the test molded product A was cracked or cracked at the portion in contact with ethyl alcohol was defined as the critical strain value.
<Examples 1-6>
Polymethyl methacrylate (PMMA: “Acrypet VH001” manufactured by Mitsubishi Rayon Co., Ltd., elastic modulus 3.3 GPa, density 1.2 g / cm ³ ), granular additive polytetrafluoroethylene (PTFE) resin powder (manufactured by Kitamura Co., Ltd. “ KTL-20N "elastic modulus 300 MPa average particle diameter 20 μm density 2.1 g / cm ³ ), and the following fibers A to C:
Fiber A: Wollastonite (“SH-600” manufactured by Kinsei Matec Co., Ltd.) Fiber length 35 μm Fiber diameter 1.5 μm Density 2.9 g / cm ³
Fiber B: Potassium titanate whisker (“Tismo-D” manufactured by Otsuka Chemical Co., Ltd., fiber length 15 μm, fiber diameter 0.5 μm, density 3.3 g / cm ³ )
Fiber C: Aluminum borate whisker (“Arbolex YS2” manufactured by Shikoku Kasei Kogyo Co., Ltd. Fiber length 20 μm Fiber diameter 0.75 μm Density 3.3 g / cm ³ )
Were blended in the amounts shown in Table 1, heated and mixed under a temperature condition of a cylinder temperature of 250 ° C. using a biaxial kneader, cooled, and cut to prepare pellets for molding an acrylic resin composition.

The molding pellets thus prepared were injection molded at a cylinder temperature of 245 ° C. using an injection molding machine to obtain a molded article for testing. About this molded article, Charpy impact strength and chemical crack resistance were measured. The results are shown in Table 1.
<Comparative Example 1>
A molding pellet made of only PMMA used in Example 1 is prepared under the same conditions as in Example 1, and then the prepared molding pellet is injection molded at a cylinder temperature of 245 ° C. using an injection molding machine. Thus, a molded product of Comparative Example 1 was obtained. About this molded article, Charpy impact strength and chemical crack resistance were measured. The results are shown in Table 1.
<Comparative Examples 2 and 3>
Without blending the fibers, the PMMA and granular PTFE used in Example 1 were blended in the amounts shown in Table 1, and the molding pellets were prepared under the same conditions as in Example 1. Then, the prepared molding pellets were The molded articles of Comparative Examples 2 and 3 were obtained by injection molding using an injection molding machine at a cylinder temperature of 245 ° C. About this molded article, Charpy impact strength and chemical crack resistance were measured. The results are shown in Table 1.
<Comparative Example 4>
Without blending granular PTFE, the PMMA and fiber A used in Example 1 were blended in the amounts shown in Table 1, and the molding pellets were prepared under the same conditions as in Example 1. The molded article of Comparative Example 4 was obtained by injection molding using an injection molding machine at a cylinder temperature of 245 ° C. About this molded article, Charpy impact strength and chemical crack resistance were measured. The results are shown in Table 1.

<Comparative Example 5>
PMMA used in Example 1 and spherical silica (“FB-20” manufactured by Denki Kagaku Kogyo Co., Ltd., particle size 20 μm, density 2.2 g / cm ³ ) were blended in the amounts shown in Table 1, and the same conditions as in Example 1 The molded pellets of Comparative Example 5 were obtained by injection-molding the prepared pellets at a cylinder temperature of 245 ° C. using an injection molding machine. About this molded article, Charpy impact strength and chemical crack resistance were measured. The results are shown in Table 1.

  As shown in Table 1, Examples 1 to 6 were prepared by blending granular PTFE having a modulus of elasticity of 15% or less of PMMA with fibers, wollastonite, potassium titanate whisker, and aluminum borate whisker. Compared with the comparative example 1 of PMMA alone, the impact resistance and chemical crack resistance were significantly improved.

  On the other hand, in Comparative Examples 2 and 3 in which only granular PTFE was blended with PMMA, the impact resistance and the chemical crack resistance were improved, but the degree was small compared to the Examples, and the impact resistance. If a large amount is added to improve chemical crack resistance, sufficient hardness cannot be obtained.

  Moreover, although the thing of the comparative example 4 which mix | blended only the fiber with PMMA improved a little impact resistance, the improvement of the chemical crack resistance was not seen.

  Moreover, in the thing of the comparative example 5 which mix | blended the granular silica with PMMA, neither the improvement of impact resistance nor the improvement of the chemical crack resistance was seen.

It is a figure explaining the test method of chemical crack resistance.

Claims (7)

  An acrylic resin composition comprising: an acrylic resin; a granular additive having an elastic modulus of 15% or less of the acrylic resin; and a fiber.   2. The acrylic resin composition according to claim 1, wherein the ratio between the average length of the fibers and the average particle diameter of the granular additive is in the range of 1/3 to 2. 3.   The content of the granular additive is 10% by volume or less with respect to the entire acrylic resin composition, and the content of the fiber is in the range of 1/3 to 2 times by volume with respect to the granular additive. The acrylic resin composition according to claim 1 or 2.   The acrylic resin composition according to any one of claims 1 to 3, wherein an average particle diameter of the particulate additive is 25 µm or less.   The acrylic resin composition according to any one of claims 1 to 4, wherein the ratio of the average diameter and the average length of the fibers is 1/10 or less.   The acrylic resin composition according to any one of claims 1 to 5, wherein the particulate additive is a polytetrafluoroethylene resin.   The acrylic resin composition according to any one of claims 1 to 6, wherein the acrylic resin is polymethyl methacrylate.

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