JPS5910386B2 - Manufacturing method for resin molded product with pearlescent luster - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a resin molded article having pearlescent luster.

More specifically, a graft polymer obtained by polymerizing any one or more of an aromatic vinyl compound, a vinyl cyanide compound, and a methacrylic acid ester in the presence of polyvinyl acetate, or a graft polymer and a styrene resin. The present invention relates to a method for producing a resin molded product having a pearlescent luster, which is produced by molding a resin material, which is a resin mixture, to give a molded product that has a silk-like soft feel and has a different shade of color depending on the viewing angle.
Conventionally, a known method for imparting pearlescent luster to thermoplastic resin molded articles is to add pearlescent pigments, such as fish scale foil, lead sulfate, lead arsenate, zinc phosphate, etc., to resin, etc., and conduct cross-dispersion. However, the molded products produced by this method have a rather metallic luster, and do not have the soft, subtle luster that natural pearls have.

Furthermore, the lead-based pigment is toxic and is therefore undesirable from a food hygiene perspective, and the fish scale foil is unfavorable because it has poor heat resistance.
Another method for obtaining a resin molded product having a pearl-like luster is to extrude or injection mold a resin composition consisting of a styrene resin and a methyl methacrylate resin, or a resin composition consisting of a polycarbonate and a methyl methacrylate resin. It is known that molded products with pearlescent luster can be obtained by using this method.

However, in the former composition consisting of styrene resin and methyl methacrylate resin, both resins have poor compatibility, and molded products using this composition have significantly poor mechanical strength.
It has drawbacks such as cracking when immersed in alcohol. The latter polycarbonate composition is
It requires high temperatures for molding and has poor workability.

Furthermore, the fact that they are expensive is particularly problematic. Therefore, the present inventors have discovered a method of molding using a material consisting of polyvinyl acetate and styrene resin as a method of producing a pearlescent resin molding that is inexpensive and has good molding workability. does not have sufficient heat resistance during molding, hardness,
It was found that the abrasion resistance and alcohol resistance were insufficient, and as a result of repeated improvements in these points, the present invention as described below was completed.

That is, the present invention relates to a graft polymer obtained by polymerizing at least one monomer selected from the group consisting of aromatic vinyl, vinyl cyanide, and methacrylic acid ester in the presence of polyvinyl acetate, or the graft polymer as described above. A resin material that is a resin mixture consisting of a styrene resin and a styrene resin, wherein the content of polyvinyl acetate in the resin material is 3 to 20% by weight.
A resin molded article having pearlescent luster is provided by molding using a resin composition consisting of the following ingredients and appropriate amounts of desired compounding agents.

The resin composition defined in the present invention has good moldability,
By melt-molding this composition, the color tone of the molded product changes subtly depending on the viewing angle, and a fine and beautiful silk-like pearlescent luster is developed.

The molded product of the present invention has better mechanical strength, surface hardness, and abrasion resistance than those using a simple mixed composition of polyvinyl acetate, and the molded product of the present invention does not cause cracks even when immersed in alcohol. do not have. The polyvinyl acetate used in the present invention may be in the form of an emulsion, granules or powder, but emulsion is particularly preferred. Polyvinyl acetate is preferably a homopolymer, but polyvinyl acetate contains 20% by weight or less of acrylic acid, methacrylic acid and their alkyl esters, and other non-containing substances such as styrene, acrylonitrile, vinyl chloride, vinylidene chloride, ethylene, and propylene. Copolymerization of saturated vinyl compounds may be used, but if the amount of copolymerization of unsaturated vinyl compounds exceeds 20% by weight, the pearlescent luster of the molded product will gradually be lost, which is not preferred.

The graft polymer of the present invention is obtained by grafting at least one monomer selected from the group consisting of aromatic vinyl, vinyl cyanide, and methyl methacrylate in the presence of the polyvinyl acetate using a radical polymerization initiator. Obtained by polymerization.

The ratio of polyvinyl acetate and the monomer to be grafted is not particularly limited, but preferably polyvinyl acetate 3-90
97-10% by weight, more preferably 9% by weight of the monomer to be grafted, more preferably 3-60% by weight
It is 7 to 40% by weight. Graft polymerization may be carried out by emulsion polymerization, suspension polymerization or bulk polymerization, but
The effects of the present invention are particularly favorable in emulsion polymerization.

Further, the polymerization is carried out at a temperature of 0 to 80° C. under normal pressure or increased pressure, which is applied in polymerization using a general radical polymerization initiator. Further, as the aromatic vinyl, styrene, alpha-methylstyrene, vinyltoluene, etc. can be used alone or in combination, and styrene is particularly preferred industrially.

As the vinyl cyanide, acrylonitrile, methacrylonitrile, vinylidene cyanide, etc. can be used alone or in combination, and acrylonitrile is particularly preferred industrially.

Further, as the methacrylic acid ester, methyl methacrylate, ethyl methacrylate, propyl methacrylate, etc. can be used alone or in combination, and ethyl methacrylate is particularly preferred from an industrial standpoint.

As the monomer to be grafted, in addition to one or more essential monomers selected from the above aromatic vinyl, vinyl cyanide, and methacrylate, optionally methyl acrylate,
Even if a copolymerizable monomer such as ethyl acrylate is used in an amount of 30% by weight or less of the total amount of monomers to be grafted, the effects of the present invention will not be impaired in any way. A particularly important requirement in the present invention is that the content of polyvinyl acetate in the resin material is 3 to 2.
0% by weight, preferably 4 to 16% by weight.

Therefore, the content of the resin part excluding polyvinyl acetate in the resin material is 97 to 80% by weight, preferably 96 to 84% by weight.
Must. The proportion of polyvinyl acetate is 3% by weight
less than 97%, i.e. the content of resin excluding polyvinyl acetate is
If the content exceeds 20% by weight, the pearlescent luster of the molded product will not be sufficiently developed. is not preferable because the molded product has insufficient surface hardness, abrasion resistance, and alcohol resistance.

The molded product of the present invention can be produced by using only a graft polymer having a polyvinyl acetate content of 3 to 20% by weight as the resin material, or by using a graft polymer having a relatively high polyvinyl acetate content as the resin material. It is also possible to use a resin mixture containing a separately produced styrene resin and a polyvinyl acetate content of 3 to 20% by weight.

The styrenic resin to be blended contains at least 50% aromatic vinyl such as styrene and alpha methyl styrene.
Polystyrene, styrene-acrylonitrile copolymer, styrene-acrylonitrile copolymer obtained by polymerizing monomers containing % by weight or more
Methyl methacrylate copolymers and the like are used, and homopolymers and copolymers in the form of powder or pellets, which are generally commercially available as styrene resins, are used. The resin composition of the present invention is
At the time of molding, appropriate amounts of compounding agents such as antioxidants, stabilizers, colorants, lubricants, fillers and reinforcing agents are added to the resin material as necessary.

After sufficiently kneading the resin composition of the present invention, the mechanical strength, surface hardness, and abrasion resistance intended by the present invention can be improved by molding it into a desired shape using an ordinary molding machine, especially an injection molding machine. A fine, beautiful, silk-like, pearlescent molded product is obtained.

The present invention will be explained below with reference to Examples.

Note that parts and percentages in the examples are based on weight unless otherwise specified. Example 1 Using 100 parts of vinyl acetate, 1 part of sodium lauryl sulfate, 0.1 part of potassium persulfate, and 200 parts of ion-exchanged water,
Emulsion polymerization was carried out at a reaction temperature of 50°C according to a conventional method to obtain an emulsion containing polyvinyl acetate having rubber-like elasticity.

Next, 20 parts of polyvinyl acetate, 60 parts of styrene, 20 parts of acrylonitrile, 0.5 part of potassium oleate, 0.24 part of tertiary dodecylmercabutane, 0.05 part of potassium persulfate, and ion exchange, which are contained in the above emulsion state, are added. Styrene and acrylonitrile were grafted onto polyvinyl acetate by emulsion polymerization using 160 parts of water at a reaction temperature of 50°C, and then 0.5 parts of aluminum sulfate was added to 100 parts of water.
A powdery graft polymer was obtained by coagulating and drying with a solution dissolved in 0 parts.

The graft polymer obtained as above and the styrene resin were blended in the proportions shown in Table 1, and in addition, 0.25 part of anthraquinone red dye (manufactured by Dainippon Ink) and 0.5 part of calcium stearate ( (manufactured by Toa Rika), mixed uniformly with a pen shell mixer, pelletized with an extruder, and then processed with an in-line screw injection molding machine at a molding temperature of 180°C and an injection pressure of 840K.
'Nogo, injection speed 301Lm/SeC, wall thickness 5m71
A L flat plate was molded.

For comparison, polyvinyl acetate obtained by coagulating and drying the emulsion containing polyvinyl acetate and a commercially available styrene resin were blended so that the polyvinyl acetate content was in the ratio shown in Table 1, and then 0.25 part of red dye and 0.5 part of calcium stearate were added and molded in the same manner as above to obtain a flat plate.

The flat plate molded products obtained all exhibited pearlescent luster with a characteristic soft silk-like luster.

The flat plate molded product was then tested for Rockwell hardness, abrasion resistance, and alcohol resistance. The results are shown in Table 1. As is clear from the results in Table 1, the resin molded product obtained by mixing and molding the graft polymer obtained by grafting styrene and acrylonitrile onto polyvinyl acetate according to the present invention is simply polyvinyl acetate. Compared to a molded product obtained by mixing a styrene resin, the molding processability, abrasion resistance, hardness, and alcohol resistance are significantly improved, and the product exhibits pearlescent properties with a soft silky luster.

Example 2 40 parts of the same polyvinyl acetate as used in Example 1,
45 parts of styrene, 15 parts of acrylonitrile, 0.3 parts of potassium oleate, 0.1 part of tertiary dodecyl mercaptan
8 parts, 0.05 parts of potassium persulfate, and 1 part of io7-exchanged water.
Table 2 shows the results of evaluating molded products in the same manner as in Example 1 using the graft polymer obtained in the same manner as in Example 1 using 20 parts and the styrene resin.

Table Example 3 Using 90 parts of vinyl acetate, 10 parts of methyl methacrylate, 1.5 parts of sodium lauryl sulfate, 0.1 part of potassium persulfate and 200 parts of ion-exchanged water, a reaction temperature of 50° C. was prepared according to a conventional method. Emulsion polymerization was then carried out to obtain a vinyl acetate copolymer having rubber-like elasticity.

Next, 60 parts of the above copolymer, 3 parts of methyl methacrylate
5 parts, 5 parts of ethyl acrylate, 0 parts of sodium lauryl sulfate
．． using 3 parts, 0.2 parts of tertiary dodecyl mercaptan, 0.05 parts of potassium persulfate, and 100 parts of ion-exchanged water.
After emulsion graft polymerization at a reaction temperature of 50° C., the mixture was coagulated and dried in the same manner as in Example 1 to obtain a powdery graft polymer. The graft polymer and styrene resin obtained as described above were mixed in the same manner as in Example 1, and the molded products were evaluated in the same manner as in Example 1. The results are listed in Table 3. .

Example 4 10 parts of the same vinyl acetate polymer used in Example 1, 70 parts of styrene, 20 parts of acrylonitrile, 0.5 part of potassium oleate, and 0.5 parts of tertiary dodecyl mercaptan.
27 parts, potassium persulfate 0.05 part and ion exchange water 2
A powdery graft polymer was obtained in the same manner as in Example 1 except that 00 parts were used.

To 100 parts of the graft polymer thus obtained, 0.25 parts of anthraquinone red dye and 0 parts of calcium stearate.
．． 5 parts were added, uniformly mixed using a pen shell mixer, and pelletized using an extruder under the same conditions as in Example 1. The pellets were then molded into a flat plate with a wall thickness of 51 g using an injection molding machine. For comparison, the polyvinyl acetate used in the present invention was coagulated with a solution of 0.5 parts of aluminum sulfate and 1000 parts of water, and the dried polymer was combined with 25 parts of acrylonitrile, 75 parts of styrene, and 1 part of potassium oleate. After emulsion polymerization using 0.5 parts of tertiary dodecyl 2 remercaptan, 0.1 part of potassium persulfate, and 200 parts of ion-exchanged water at a reaction temperature of 50°C, 0.5 parts of aluminum sulfate was added. Regarding a product in which vinyl acetate polymer is simply mixed with a powder polymer that is coagulated with a solution dissolved in 1000 parts of water and dried, such that the content of vinyl acetate polymer in the resin material is 10%. evaluated. The above results are shown in Table 4.

Example 5 15 parts of the same vinyl acetate polymer used in Example 1, 65 parts of styrene, 20 parts of acrylonitrile, 0.5 part of potassium oleate, and 0.5 parts of tertiary dodecyl mercaptan.
17 parts, potassium persulfate 0.05 part and ion exchange water 2
A powdery graft polymer was obtained in the same manner as in Example 1 except that 0.00 parts was used.

The thus obtained graft polymer was evaluated in the same manner as in Example 4. For comparison, using the same sample as in the comparative example of Example 4 and operating in the same manner, vinyl acetate polymer was simply mixed so that the content of vinyl acetate polymer in the resin material was 15%. I evaluated things.

Claims (1)

[Claims] 1. A graft polymer obtained by polymerizing at least one monomer selected from the group consisting of aromatic vinyl, vinyl cyanide, and methacrylic acid ester in the presence of polyvinyl acetate, or a styrene-based graft polymer and the above graft polymer. Molding using a resin material that is a resin mixture consisting of a resin and a resin composition in which the content of polyvinyl acetate in the resin material is 3 to 20% by weight and an appropriate amount of a desired compounding agent. A method for producing a resin molded article having pearlescent luster.