JP5016265B2 - Methacrylic resin composition - Google Patents

Description

  The present invention relates to a methacrylic resin composition capable of obtaining a molded article having improved impact resistance.

  Methacrylic resin (polymethyl methacrylate: PMMA) has the highest hardness among thermoplastic resins and is excellent in chemical resistance against acids, alkalis, and the like, and is therefore widely used in various molded products. However, since PMMA has a relatively low impact resistance and the cracked surface may be sharp when it is cracked, it must be used with care. Furthermore, PMMA has a problem that when a solvent acts, the solvent attacks a portion having a large residual strain to cause a chemical stress phenomenon, and so-called chemical cracks are likely to occur.

Therefore, it has been practiced to improve the chemical crack resistance by increasing the impact resistance of PMMA by adding a rubber such as acrylic rubber to PMMA and reducing the residual strain (see, for example, Patent Document 1). ).
JP 09-059472 A

  However, when rubber is blended with PMMA, the strength and hardness are reduced as compared with the case of PMMA alone, and the dimensional change due to temperature is increased, resulting in a problem that dimensional stability is lowered. In addition, when fastening screws such as tapping screws to a molded product, PMMA has a problem that squeak noise is likely to occur when this screw is tightened. It was not made.

  The present invention has been made in view of the above points, and can improve impact resistance without reducing strength, hardness, and dimensional stability, and reduce squeak noise during screw tightening. An object of the present invention is to provide a methacrylic resin composition that can be used.

Main methacrylic resin composition of the present invention, methacrylic resin, a resin composition obtained by blending a powder of calcined treated fluororesin powder of the calcined fluorine-based resin, 420 ° C. The mass reduction rate when heated for 30 minutes is 5% by mass or more and 10% by mass or less .

According to the present invention, by incorporating a powder of the calcined treated fluorine-based resin, the strength and hardness without lowering the dimensional stability, it is possible to improve impact resistance, also screws tightening It is possible to reduce a squeak noise at the time.
Further, by using such a fluororesin powder, chemical crack resistance can be improved.

Oite this onset Akira, powder of the fluorine-based resin is preferably a powder of polytetrafluoroethylene.

  Polytetrafluoroethylene powder can be easily and inexpensively obtained, and the above-described effects can be obtained with high efficiency.

  According to the present invention, by blending the fired fluororesin powder, impact resistance can be improved without reducing strength, hardness and dimensional stability, and screw tightening can be achieved. The squeak noise can be reduced.

  Hereinafter, the best mode for carrying out the present invention will be described.

  In the present invention, powder of fluororesin is blended with methacrylic resin (polymethyl methacrylate: PMMA). By blending the fluororesin powder with PMMA, the stress can be relieved and the occurrence of cracks can be dispersed to improve the impact resistance.

  Examples of the fluororesin include tetrafluoroethylene resin (PTFE), tetrafluoroethylene / perfluoroalkoxyethylene copolymer resin (PFA), tetrafluoroethylene / hexafluoropolypropylene copolymer resin (FEP), and tetrafluoroethylene resin. And ethylene-ethylene copolymer resin (ETFE), vinylidene fluoride resin (PVF), chlorotrifluoroethylene resin (PCTFE), and ethylene-chlorotrifluoroethylene resin (ECTFE).

  And in this invention, what was baked as a powder of a fluororesin is used. The baked fluororesin powder is commercially available as a lubricant additive and can be used.

  When a non-fired fluororesin powder is used, when the fluororesin powder is blended with PMMA and kneaded, the fluororesin powder is fibrillated, and the fluororesin powder is PMMA. It is difficult to obtain a moldable resin composition because the body cannot be dispersed, and the fluorine resin powder is not uniformly dispersed in PMMA. It is not possible to obtain a sufficient effect. For this reason, in the present invention, a fluororesin powder is fired to increase the thermal history, and a resin composition is obtained in which the fluororesin powder is uniformly dispersed in PMMA without causing fiberization. It is what.

  In the present invention, it is preferable to use a fluorinated resin powder having a mass reduction rate of 5% by mass or more when heated at 420 ° C. for 30 minutes. Powders with small heat loss tend to have relatively high molecular weight and are relatively hard, and the effect of reducing the residual stress of PMMA molded products due to the blending of fluororesin powder is reduced, and the chemical crack resistance of the molded products The effect of improving is also insufficient. For this reason, the chemical crack resistance of the molded product is obtained by blending PMMA with a fluorine resin powder having a mass reduction rate of 5% by mass or more when heated at 420 ° C. for 30 minutes and having a thermal history that is not too high. It is intended to increase. The upper limit of the mass reduction rate when the fluororesin powder is heated at 420 ° C. for 30 minutes is not particularly set, but is practically preferably 10% by mass or less.

  The powder of the fluororesin is not particularly limited, but those having an average particle diameter in the range of 1 to 70 μm are preferable. When the average particle size is less than 1 μm, the handleability is deteriorated and uniform mixing becomes difficult. On the other hand, if the average particle size exceeds 70 μm, the particles become coarse, which may appear on the surface of the molded product and impair the appearance.

  And the methacrylic resin composition of this invention can be obtained by mix | blending the powder of the fluorine-type resin by which baking processing was carried out to PMMA, and mixing and knead | mixing this.

  Here, the blending amount of the fluororesin powder is not particularly limited, but a range of 0.5 to 5% by mass (0.5 to 5 parts by mass with respect to 100 parts by mass of PMMA) is preferable. When the blending amount of the fluororesin powder is less than 0.5% by mass, the effect of improving the impact resistance by blending the fluororesin powder cannot be sufficiently obtained. If the blending amount exceeds 5 mass%, the bending strength decreases greatly. Therefore, the blending amount of the fluororesin powder is preferably 5 mass% or less.

  A molded product can be obtained by molding the methacrylic resin composition of the present invention obtained as described above by any molding method such as injection molding. Here, the temperature when mixing and kneading the fluororesin powder in PMMA and the temperature during molding are higher than the melting temperature of PMMA and lower than the melting temperature of the fluororesin powder as described above. The temperature is set.

  In this molded product, since the PMMA contains a fluorinated resin powder that has been fired, the impact resistance of the molded product can be increased by the flexible fluororesin powder. Is. In addition, the fluororesin powder does not significantly reduce the hardness and strength of the molded product unlike rubber, and does not decrease the dimensional stability.

  Next, the present invention will be specifically described with reference to examples.

( Comparative Example 1 )
As PMMA, “Acrypet VH001” manufactured by Mitsubishi Rayon Co., Ltd. was used. As the fluorine resin powder, a fired “KTL-450” manufactured by Kitamura Co., Ltd. was used. After heating this fired PTFE powder to 420 ° C. at a temperature rising temperature of 10 ° C./min, the loss on heating was measured with a TGA apparatus when this temperature was maintained for 30 minutes. Met.

  Then, a PTFE powder is blended with PMMA at a blending amount of 2% by mass, heated and kneaded at a cylinder temperature of 300 ° C. using a biaxial kneader, cooled, and pulverized to form a methacrylic resin composition. A pellet was prepared.

  The molding pellets thus prepared were injection-molded using an injection molding machine at a cylinder temperature of 245 ° C. to obtain a test molded product.

(Example 1 )
As the fluorine-based resin powder, a fired “KTL-20N” manufactured by Kitamura Co., Ltd. was used. After heating this fired PTFE powder to 420 ° C. at a temperature rising temperature of 10 ° C./min, the loss on heating when this temperature was maintained for 30 minutes was measured with a TGA apparatus, and it was 6% by mass. Met.

Others, in the same manner as in Comparative Example 1 to prepare a molding pellets of the methacrylic resin composition, by injection molding in the same manner as in further comparative Example 1, to obtain a molded article for testing.

(Comparative Example 2 )
As PMMA, “Acrypet VH001” manufactured by Mitsubishi Rayon Co., Ltd. was used as it was, and injection molding was carried out in the same manner as in Comparative Example 1 to obtain a molded product for testing.

(Comparative Example 3 )
As PMMA, “Acrypet IR D30 001” (impact resistant grade with rubber added) manufactured by Mitsubishi Rayon Co., Ltd. is used as it is, and injection molding is performed in the same manner as in Comparative Example 1 to obtain a molded product for testing. It was.

(Comparative Example 4 )
As the fluororesin powder, “Teflon (registered trademark) 7A-J” manufactured by Mitsui DuPont Fluorochemical Co., Ltd., which has not been fired, was used.

In the same manner as in Comparative Example 1 , when this untreated PTFE powder was mixed with PMMA and heated and kneaded with a biaxial kneader, the PTFE powder could not be fiberized and dispersed, and could be used for molding. A pellet could not be obtained.

For Example 1 above 及 beauty Comparative Example 1 to 3 obtained test moldings, pencil hardness (JIS K 5400), flexural strength (JIS K 7171), Charpy impact strength (JIS K 7111), the linear expansion coefficient ( ASTM D696), chemical crack resistance, and the presence or absence of squeaking noise when tightening screws. The results are shown in Table 1.

  The chemical crack resistance test was conducted as follows. As shown in FIG. 1, using a jig 2 having a convex curved surface 1, 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. 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. A strain of 0.6% was 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 is used. Four types of distortion were applied.

  Next, the cylindrical body 4 having an inner diameter of 5 mm that opened at the top and bottom was fixed to the upper surface of the central portion of the test molded product A with silicon grease, and the cylindrical body 4 was filled with ethyl alcohol and left for 24 hours. Table 1 shows the critical strain values when the test molded product A is cracked or cracked at the portion where ethyl alcohol is brought into contact.

  In addition, the test for squeak noise when tightening screws is performed by checking whether or not a squeak noise is generated when a drill with a diameter of 3.4 mm is drilled in a test product having a thickness of 3 mm and a T4 tapping screw is tightened with a screwdriver. It was done by confirming.

As seen in Table 1, of those real Example 1 blended with PTFE powder was calcined in PMMA, Charpy impact strength than Comparative Example 2 PMMA-free formulation is greatly improved, also impact grade It is confirmed that Charpy impact strength equal to or higher than that of PMMA Comparative Example 3 is obtained. On the other hand, the pencil hardness real Example 1, the flexural strength, linear expansion coefficient is equivalent to Comparative Example 1-2, the hardness, strength, dimensional stability is confirmed that no decrease. Furthermore, those real Example 1 and Comparative Example 1 is also confirmed that creaking sound at the time of screwing does not occur.

Moreover, as seen in the actual Example 1, by using those heating loss is more than 5 mass% as a sintering treated PTFE powder, critical strain value is increased, it confirmed that the resistance to chemical crack resistance is improved Is done.

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

Claims (2)

A resin composition comprising a methacrylic resin mixed with a fired fluororesin powder , wherein the fired fluororesin powder has a mass reduction rate when heated at 420 ° C. for 30 minutes. Is a methacrylic resin composition characterized in that it is 5 mass% or more and 10 mass% or less . The methacrylic resin composition according to claim 1, wherein the fluororesin powder is a polytetrafluoroethylene powder.

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