JPS631345B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyacetal resin composition for surface processing which has excellent thermal stability. Plastics are generally extremely stable chemically, and molded products made by ordinary injection molding have smooth surfaces. Difficult to process. In particular, polyacetal resin has poor surface activity and there are no suitable solvents that have affinity for it, so surface decoration and adhesion are difficult.
Currently, it is hardly used in applications that require such processing. Looking at it from the other side, polyacetal resins have excellent mechanical properties, so they are often used mainly for mechanical parts, and it can be said that there has not been much demand for surface decoration etc. in the past. However, recently the applications of plastics are diverse.
In addition, there has been a strong tendency for products to become more sophisticated, and there are often cases where multiple performances, such as functionality and appearance, or functionality and adhesiveness, which were not always required to be compatible in the past, are required at the same time. In this way, polyacetal resins are increasingly being used in many cases where good surface workability is required. Although it cannot be said that there has been much research into ways to improve the surface workability of polyacetal resins, for example, it is possible to improve the surface workability to some extent by treating the surface of a molded product with an acidic or oxidizing liquid. p-toluenesulfonic acid, camphor sulfonic acid, phosphoric acid, acidic ammonium sulfate, etc. have been proposed as acidic liquids, and a chromium sulfuric acid mixture has been proposed as oxidizing liquids. The purpose of treatment with these liquids is to chemically erode the surface of the polyacetal resin molded product to create a rough surface, and also to form active reactive groups in some polyacetal molecules through its oxidizing action. It is thought that the purpose is to make
Generally, when such surface treatment is attempted to sufficiently enhance the surface treatment effect, problems such as overall deterioration of the polyacetal resin molded product, which is the base material, or the occurrence of cracks occur. On the other hand, if the treatment conditions do not cause deterioration of the base material, the surface treatment effect will be insufficient and good surface treatment will not be possible. For this reason, polyacetal resin molded products with surface workability suitable for practical use have not been known until now. In order to obtain a polyacetal resin molded product with excellent surface workability, the present inventors conducted extensive studies on polymer compositions, and as a result, they developed a composition consisting of a polyacetal resin, a metal salt from group 3 of the periodic table, and a certain type of polymer. It has been found that this material exhibits excellent thermal stability and plating resistance. That is, the present invention provides (a) polyacetal resin
100 parts by weight, (b) 2 to 35 parts by weight of a powder having an average particle size in the range of 0.1 to 4.0 microns of a carbonate, phosphate, acetate or a mixture thereof of a group metal of the periodic table, and (c ) Unsaturated polyesters, alkyl esters of acrylic acid or methacrylic acid, amides of acrylic acid or methacrylic acid, triallyl cyanurate, diallyl phthalate, polymers or copolymers of compounds selected from the group of vinyl acetate and divinylbenzene, or the like. mixture of 0.01~
The present invention relates to a polyacetal resin composition for surface treatment, which is composed of 20 parts by weight and has excellent thermal stability. In the present invention, the purpose of incorporating various salts of Group Group metals in the periodic table into the polyacetal resin is to easily form a roughened surface suitable for surface processing. In other words, when various salts of group metals of the periodic table are dispersed in the polyacetal continuous phase,
They are easily decomposed and removed by a suitable acid, leaving traces as a roughened surface. Among the various salts of Group Group metals of the periodic table used in the present invention, examples of preferable carbonates include calcium carbonate, magnesium carbonate, carbonate, and barium carbonate, with calcium carbonate being the most preferable. Furthermore, in surface treatments such as plating, the specularity of the surface and the adhesion between the plating metal and the resin are often fundamentally important characteristics. In addition, good thermal stability during molding is sometimes strictly required. The present inventors investigated the relationship between these characteristics and the average particle size of various salts of group metals of the periodic table, and found that metal salts with an average particle size exceeding 4.0 microns deteriorate specularity and adhesion. , while the average particle size
Metal salts smaller than 0.1 micron were found to reduce adhesion and thermal stability. Therefore, when specularity, adhesion, and thermal stability are taken into account, the average particle diameter of the various salts of Group Group metals of the periodic table is preferably in the range of 0.1 to 4.0 microns, particularly 0.5 to 2.0 microns. In addition, if the weight of the various salts of group metals of the periodic table contained is small, the effect of improving surface workability will not appear, and if it is too large, not only will the mechanical properties of the polyacetal resin deteriorate, but also the effect of improving surface workability will not appear. On the contrary, it will decrease, and the thermal stability during molding will also worsen, so if you consider the balance of these,
The amount is preferably 2 to 35 parts by weight based on 100 parts by weight of the polyacetal resin. On the other hand, the present inventors conducted various studies on this polyacetal resin composition, that is, a composition in which various salts of metals of Group Group of the Periodic Table were added to the polyacetal resin in the above-mentioned average particle diameter and amount. When etching with suitable acids, i.e. acidic or oxidizing liquids, particularly strong acidic liquids,
In strong oxidizing liquids, the molded product itself cracks,
The specularity and mechanical performance of the plated product may deteriorate significantly, and depending on the composition, if the molding conditions during molding are not carefully controlled, the molded product may discolor or the polyacetal resin may thermally decompose in the molded product. It has become clear that decomposition gas can leave traces of decomposition gas. In order to solve these problems, the present inventors further investigated and found that the above-mentioned polyacetal resin composition further contains unsaturated polyester, an alkyl ester of acrylic acid or methacrylic acid, an amide of acrylic acid or methacrylic acid,
It has been found that the above problem can be eliminated by containing component (c) which is a polymer, copolymer or a mixture thereof of a compound selected from triallyl cyanurate, diallyl phthalate, vinyl acetate and divinylbenzene. It is something. The reason for including component (c) is as described above. The unsaturated polyester is provided in the form of an unsaturated polyester prepolymer alone or in the form of a mixture thereof with a crosslinking agent consisting of a vinyl monomer or a prepolymer having an unsaturated residue thereof. Unsaturated polyester prepolymers include unsaturated dicarboxylic acids, or combinations of saturated dicarboxylic acids and saturated unsaturated monocarboxylic acids;
A product obtained by esterifying a polyhydric alcohol or a combination thereof with a monohydric alcohol is used. Examples of acids used in the production of unsaturated polyester prepolymers include unsaturated dicarboxylic acids such as maleic acid, maleic anhydride, fumaric acid,
Examples include itaconic acid, citraconic acid, endomethylenetetrahydrophthalic acid, and saturated dicarboxylic acids such as orthophthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, and adipic acid. Mixtures of two or more of these can also be used. Examples of monocarboxylic acids include acetate, propionic acid, butyric acid, benzoic acid, acrylic acid, methacrylic acid, and mixtures of two or more of these acids may also be used. The above carboxylic acids may also be provided in the form of alkyl esters such as methyl esters and dimethyl esters. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, butanediol, diethylene glycol, dipropylene glycol,
Glycerin, trimethylolpropane, etc., and monohydric alcohols such as methanol, ethanol, allyl alcohol, etc. are used. As the crosslinking agent, the compound used as the component (c) of the present invention is used, but in addition to that, styrene, α-
Examples include methylstyrene, vinylpyridine, vinylpyrrolidone, and vinyl propionate. The amount of the crosslinking agent other than component (c) mentioned above is preferably in the range of 0.2 to 1.0 times the weight of the unsaturated polyester prepolymer.
It is not more than 5 parts by weight. In the present invention, the above polymer contained in the polyacetal resin together with various salts of group metals of the periodic table is an essential component of the present invention. To summarize the purpose again, as mentioned above, it prevents cracks from forming in the molded product even when etching with particularly strong acidic liquids and strong oxidizing liquids, and
This is to prevent a decrease in thermal stability during molding when the polyacetal resin contains various salts of Group Group metals of the periodic table. The reason for preventing cracking during etching is not clear, but when polyacetal resin contains various salts of group metals of the periodic table, the composition becomes hard and internal strain increases. It is thought that the further presence of , due to its plasticizing action, reduces or eliminates internal strain and prevents cracks. In addition, the amount of polymers used in the present invention varies depending on the type of polymer, and
The amount is preferably 0.01 to 20 parts by weight per 100 parts by weight. If it is less than 0.01 part by weight, the above effects cannot be obtained, and if it exceeds 20 parts by weight, the strength and other properties of the composition as a whole will be reduced. The polyacetal resin used in the present invention may be a homopolymer, that is, a polymer obtained by polymerizing formaldehyde or trioxane (including those whose terminals have been stabilized), or a polymer obtained by polymerizing formaldehyde or trioxane, or a polymer obtained by polymerizing trioxane and a cyclic ether, a cyclic It may be a binary, ternary or more copolymer obtained by copolymerizing comonomers such as acetal. The composition of the present invention includes various additives normally added to polyacetal resins, such as heat stabilizers, antioxidants, ultraviolet absorbers, antistatic agents, crystal nucleating agents,
There is no problem even if pigments are added. In order to obtain the composition of the present invention, it is preferable to mix the constituent components using equipment, such as a kneader, roll mill, or extruder, which is normally used for kneading resin melts. An extruder is most preferable from the viewpoint of blocking oxygen and working environment. The mixing temperature is above the melting point of the polyacetal resin used. This is determined by the need to uniformly mix the polyacetal resin in its molten state. The upper temperature limit is generally limited by the thermal decomposition stability of the polyacetal resin used;
Mixing is usually carried out at a temperature below 250°C, preferably below 230°C. Polymers such as unsaturated polyesters for thermal stability and crack prevention may be mixed directly as polymers, or may be added in the form of monomers or prepolymers and polymerized in an extruder. In the case of thermosetting polymers, the latter is preferred. In addition, it is preferable to premix the constituent components in advance using a tumbler or Henschel mixer, etc. in order to make a homogeneous composition, and it is preferable to use the polyacetal resin in a powdered state for stable supply to the extruder. Although preferred, these are not required. In addition, in the case of the method of adding the above-mentioned monomer or prepolymer, it is preferable to maintain a temperature at which a polymerization reaction does not occur during premixing. In the case of the above method of adding monomers or prepolymers, the heating conditions for polymerizing them are, for example, 190°C x 1 to 10 minutes, depending on the type of monomer or prepolymer. It is.
This condition can be achieved in most cases by the typical temperature and time combinations (determined by the extrusion speed) used when mixing polyacetal resin compositions using conventional extruders, or by other auxiliary heating means. However, the present invention does not impose any limitations on the heating method itself. Further, a polymerization initiator may be added to the composition. There are various ways to confirm that the polymerization of the added monomer or prepolymer is completed by the above heating and that no unreacted materials remain. There are methods for checking by odor, and further checking by immersing pellets in a solvent and checking whether unreacted substances are extracted using infrared spectrophotometry. The polyacetal resin composition of the present invention produced by the above method is usually made into a molded product using an injection molding machine (an extruder or other machine may be used depending on the shape of the molded product), and then the molded product is further molded with an appropriate acid. and is etched. As a result, a polyacetal resin molded product having the desired excellent surface workability can be obtained. Suitable acids for use in etching the polyacetal resin composition of the present invention include any acidic or oxidizing liquid that can decompose the various salts of Group Group metals of the periodic table blended as described above. However, it is preferable to use less volatile acidic or oxidizing liquids, such as aqueous sulfuric acid solution, sulfuric acid-
A mixed aqueous solution of phosphoric acid, a mixed aqueous solution of sulfuric acid and chromic acid, a phosphoric acid aqueous solution, and the like are preferred from the viewpoint of workability. The thus etched polyacetal resin molded product with excellent surface workability has a peel strength (Kg/cm) of the plating layer of 1 when plated with metal.
The polyacetal resin composition of the present invention is extremely useful as it has an adhesion strength of Kg/cm or more, usually 1.5 to 2.5 Kg/cm, and also shows surprising effects in coatings other than metal plating and bonding with adhesives. I can see the light. The present invention will be explained in more detail below with reference to Examples. Examples 1 to 13 and Comparative Examples 1 to 2 "Tenatsuku 5010" as polyacetal resin
(Manufactured by Asahi Kasei Corporation, acetal homopolymer,
After mixing 100 parts by weight of general grade) with 8.7 parts by weight of finely powdered calcium carbonate (Whiten SSB Red, manufactured by Shiraishi Calcium Co., Ltd., average particle size 1.25 microns) and the amount of the compound shown in Table 1 in a tumbler. The mixture was kneaded and pelletized using an extruder set at 190°C. Using this pellet, thermal stability was measured, and a 3 mm thick flat plate was produced by injection molding and used as a test material. This flat plate was degreased with 1,1,1-trichloroethane, and 96% sulfuric acid/85% phosphoric acid/water = 40/25/
Etching was carried out by immersing it in a solution consisting of 35 (weight ratio) at 40°C for 8 minutes. Next, the etched flat plate was plated using a conventional method. First, it is immersed in a pre-treatment liquid for plastic plating (manufactured by Okuno Pharmaceutical Co., Ltd., Catalyst) and an accelerator (10% aqueous hydrochloric acid solution) for a predetermined time, and then treated with a chemical plating liquid (manufactured by Okuno Pharmaceutical Co., Ltd., TMP chemical nickel plating liquid). It was chemically plated using a prescribed method and immediately subjected to electroplating. Average plating film thickness is copper 40μ, nickel 10μ,
Chrome was set to 0.1μ. The performance of the plated products plated in this manner was as shown in Table 1. The plating performance was measured using the following method. (1) Peeling strength of plated products: Make parallel cuts of 10 mm width on the plated surface, pull the plated film between the cuts in a direction perpendicular to the flat plate surface, and calculate the stress required for peeling. (2) Appearance of plated products: Visually inspect from a distance of 60 cm from the test surface under a light source of 300 lux or more. The evaluation criteria are as shown in (note) in Table 1. Table 1 shows that the polyacetal resin composition of the present invention has improved thermal stability and excellent plating performance.

【table】

[Table] Examples 14 to 17 and Comparative Examples 3 and 4 Magnesium carbonate (average 8.7 parts by weight of barium carbonate (average particle size 2μ), barium acetate (average particle size 3μ) or calcium hydrogen phosphate (average particle size 2~3μ) and as a reactive compound unsaturated polyester (Toyo Manufactured by Boseki Co., Ltd., U-Pika
A predetermined amount of CLC-834) was mixed in a tumbler and kneaded in the same manner using an extruder to form pellets. The thermal stability was measured using this pellet, and a flat plate was formed and plated in the same manner as in Example 1 to examine the performance of the plated product. The thermal stability and performance of the plated materials of these polyacetal resin compositions are shown in Table 2 (all of the metal salts mentioned above are first-grade reagents, barium acetate is used by crushing it in a mortar, and other was used as is.)

[Table] Examples 18 to 20 and Comparative Examples 5 and 6 Calcium carbonate (manufactured by Shiroishi Calcium Co., Ltd.) with various average particle sizes shown in Table 3 was added to 100 parts by weight of polyacetal resin "Tenatsuku 5010" (manufactured by Asahi Kasei Corporation). ) and 1.1 parts by weight of unsaturated polyester (manufactured by Toyobo Co., Ltd.),
The resin composition was plated in the same manner as in Example 1, and the performance of the plated product was examined. The performance of these plated products was as shown in Table 3.

【table】

[Table] * It was impossible to extrude.
※※ Applicable for applications that do not require very strict appearance.
Examples 21 to 23 and Comparative Example 7 The same etching plates used in Table 3 were used, and after etching, they were thoroughly washed with water, air-dried, and coated with acrylic paint (manufactured by Tokyo Paint Co., Ltd., Acrystar, blue). , baking treatment was performed at 150°C for 30 minutes. Cuts in a grid pattern were made in the coating film, and a peel test using Scotch tape was performed. The results are shown in Table 4.

【table】

[Table] Examples 24 to 27 and Comparative Examples 8 to 10 Same calcium carbonate as Example 1 (average particle size 1.25
Plating was carried out in the same manner as in Example 1 using a micron). However, the amount of calcium carbonate was changed as shown in Table 5, and the amount of unsaturated polyester was added in an amount equivalent to 10% of the weight of calcium carbonate. The results are shown in Table 5.

【table】

[Table] Examples 28 to 31 and Comparative Examples 11 to 12 The same experiments as Examples 25 to 27 and Comparative Examples 8 and 10 were carried out, and in Example 31, an experiment was carried out in which the amounts of calcium carbonate and unsaturated polyester were increased. "Jyuracon M90-02" as a resin
(manufactured by Polyplastics Co., Ltd., acetal copolymer, general grade). The results are shown in Table 6.

[Table] Examples 32 to 34 and Comparative Example 13 The same experiment as in Example 25 was carried out by changing the amount of unsaturated polyester added. The results are shown in Table 7.

【table】

[Table] As can be seen from the above examples, the polyacetal resin composition of the present invention has excellent thermal stability, and when the molded product is etched with an appropriate acid, an excellent surface-treated molded product can be obtained. The field of application of this resin can be further expanded, for example, it can be used as a substitute for metal in parts that require both functionality and decoration.
The effect of contributing to weight reduction and cost reduction is extremely large.

Claims (1)

[Claims] 1. (a) 100 parts by weight of polyacetal resin; (b) powder of carbonate, phosphate, acetate or a mixture thereof of a group metal of the periodic table, with an average particle size in the range of 0.1 to 4.0 microns 2 to 35 parts by weight, and (c) a polymer of a compound selected from the group of unsaturated polyesters, alkyl esters of acrylic or methacrylic acid, amides of acrylic or methacrylic acid, triallyl cyanurate, diallyl phthalate, vinyl acetate and divinylbenzene. , a copolymer or a mixture thereof. A polyacetal resin composition for surface treatment with excellent thermal stability.