JP2800663B2 - Method for producing melamine resin molded article - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a melamine resin molded article.

[0002]

2. Description of the Related Art Melamine resins are obtained by a condensation reaction between melamine and formaldehyde. A melamine resin molding material is obtained by adding a filler, a release agent, a curing aid, and the like to the obtained melamine resin varnish.

A melamine resin molding material is a thermosetting resin molding material, and is widely used as a material for various electric parts such as wiring appliances and electric appliances and tableware. This melamine resin molding material is injection molded by an injection molding machine or the like to obtain various molded products. The characteristics required for these molded products are
Low warpage and low post-shrinkage.

[0004] In order to satisfy the above requirements, a special blending and manufacturing method of the melamine resin molding material had to be used. That is, an inorganic filler is used as a special compounding of the melamine resin molding material to obtain a low warpage molded product. Reduce melamine resin content.
Reduce the content of fiber filler. Such a method was necessary.

In order to obtain a molded article having a low post-shrinkage, a special method of blending and producing a melamine resin molding material includes:
Use inorganic filler. Reduce melamine resin content. Prolong curing time. Aging the molded article. Such a method was necessary.

In order to obtain molded products having low warpage and low post-shrinkage for melamine resin molding materials such as melamine phenol resin molding materials and modified melamine resin molding materials, special blending and molding are required as described above. A method of manufacturing the product was required.

[0007] The use of a special compounding method or a method of manufacturing a molded product as described above has further increased the cost, complicated the manufacturing process, long processing time, and made the manufacturing difficult.

Therefore, there has been a demand for a melamine-based resin molded article which uses as general a composition as possible and has excellent characteristics such as low warpage and low post-shrinkage.

[0009]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide a melamine resin capable of obtaining a molded article having excellent characteristics with low warpage and low post-shrinkage. An object of the present invention is to provide a method for manufacturing a molded article.

[0010]

According to a first aspect of the present invention, there is provided a method for producing a melamine-based resin molded product, wherein a melamine-based resin molding material is injection-molded at a mold temperature of 200 to 250 ° C. .

According to a second aspect of the present invention, in the method for producing a melamine-based resin molded product, the melamine-based resin molding material contains phthalic anhydride in an amount of 0.1% based on the total amount of the melamine-based resin molding material.
It is characterized by containing 2 to 0.5% by weight.

Hereinafter, the present invention will be described in detail. Melamine resin which is a matrix resin used in the present invention, the molar ratio of formaldehyde to melamine is 1.0 to 2.0,
30 to 12 at a temperature of 60 to 100 ° C at pH 7.0 to 9.5
Obtained by performing a condensation reaction for 0 minutes. 100 parts by weight of the varnish of the obtained melamine resin, a filler such as pulp 20 to
Add 40 parts by weight and impregnate to make a melamine-penetrated product.

The melamine resin varnish is dehydrated and solidified by a dehydrator or the like to obtain a melamine solid resin.

Next, the dried melamine product obtained by drying the melamine-infiltrated product with a dryer is pulverized with a pulverizer,
For example, with respect to 100 parts by weight of the dried melamine, 0.2 to 2 parts by weight of a releasing agent such as zinc stearate, 0.2 to 0.5 parts by weight of a curing aid such as taurine and phthalic anhydride, and 0.1% by weight of a pigment. A melamine resin molding material can be obtained by adding and mixing 5 to 1.5 parts by weight, in some cases, melamine solid resin, powdered pulp, gypsum and the like, and mixing and dispersing and kneading with a ball mill, kneader or the like.

The melamine resin molding material obtained as described above is injection molded by an injection molding machine to obtain a molded product.

Usually, the mold temperature of an injection molding machine for injection molding of a melamine resin molding material is about 165 to 175 ° C., and the mold temperature is further increased to 200 to 25 ° C.
By setting the temperature at 0 ° C., it is possible to obtain a molded product excellent in characteristics with low warpage and low post-shrinkage.

The warpage is evaluated by the orientation difference, which is the difference between the molding shrinkage in the parallel direction and the perpendicular direction, and the smaller the numerical value, the better. This molding shrinkage ratio is JIS K 691
Measure based on 1. The orientation difference is about 0.2% when the mold temperature of the injection molding machine is about 165 to 175 ° C, but is 0.01 to 0.01 when the mold temperature is 200 to 250 ° C.
It is about 0.06%.

The post shrinkage is measured according to JIS K 6911, and the smaller the value, the better. After this, the shrinkage rate is 0.8 when the mold temperature is about 165 to 175 ° C. when taurine is added as a hardening agent in an amount of 0.3% by weight based on the total amount of the melamine resin molding material. %, But 0.65 when the mold temperature is 200 to 250 ° C.
About 0.7%.

The total amount of the melamine resin molding material is an amount containing the melamine resin and a filler such as pulp.

Further, by adding 0.2 to 0.5% by weight of phthalic anhydride to the total amount of the melamine resin molding material in place of the above-mentioned taurine as a curing aid, the post-shrinkage ratio becomes 0.5 to 0.5%. It becomes about 0.6%, and a molded article with further low shrinkage is obtained.

If the amount of phthalic anhydride is less than 0.2% by weight based on the total amount of the melamine resin molding material, the effect of low post-shrinkage is small, and if it exceeds 0.5% by weight, molding becomes difficult.

Regarding the bending strength, JIS K 691
It is measured based on 1, and the larger the value, the better. This bending strength, when the mold temperature is about 165 to 175 ° C,
Whereas it is 10 kgf / mm ² approximately, when the mold temperature is 200 to 250 ° C., is about 11 kgf / mm ^2.

Regarding the compressive strength, ASTM D 78
5 was measured, and the larger the value, the better. When the mold temperature is about 165 to 175 ° C.,
While it is about 20 kgf / mm ² , when the mold temperature is 200 to 250 ° C., it is about 22 kgf / mm ² .

That is, the bending strength, the compressive strength and the like are not deteriorated, and are rather excellent.

If the mold temperature is less than 200 ° C., the above-mentioned warpage and post-shrinkage characteristics are not improved due to a large amount of residual volatile components in the molded article. If the mold temperature exceeds 250 ° C., the melamine resin becomes Will be disassembled.

As described above, in order to obtain a molded product having excellent characteristics with low warpage and low post-shrinkage, the mold temperature of the injection molding machine is set at 2 ° C.
Although it is good to be 00-250 degreeC, Preferably, it is good for the mold temperature of an injection molding machine to be 215-235 degreeC.

As described above, according to the method for producing a melamine-based resin molded article of the present invention, a melamine-based resin molded article having low warpage and low post-shrinkage and excellent properties can be obtained.

[0028]

According to the present invention, when a melamine-based resin molding material is injection-molded by an injection molding machine or the like, the mold temperature is set higher than the normal mold temperature of about 165 to 175 ° C.
By setting the temperature to 0 to 250 ° C., the residual volatile matter in the molded product is reduced, so that warpage and post-shrinkage are reduced, and the characteristics are improved.

Particularly with respect to low post-shrinkage, it is preferable to use phthalic anhydride rather than taurine as a curing aid for the melamine resin molding material. That is, the decomposition temperature of taurine is 3
Decomposition temperature of phthalic anhydride is 2
At 13 ° C., in injection molding at a mold temperature of about 215 ° C., taurine does not decompose and remains in the molded product, but phthalic anhydride decomposes and no longer remains in the molded product. Shrink.

[0030]

The present invention will be described below in detail with reference to examples.

The quality of the melamine resin molded product is judged based on the molded product at a normal mold temperature of about 165 to 175 ° C., and the orientation difference, which is a warp substitution characteristic, is 0.1%.
Hereinafter, a molded product having a post-shrinkage ratio of 0.7% or less was regarded as acceptable.

The components of Examples 1 to 3 and Comparative Examples 1 and 2 were as follows: 60 parts by weight of melamine dry product, 20 parts by weight of melamine solid resin, 9 parts by weight of powdered pulp, 5 parts by weight of gypsum, stearin 1.5 parts by weight of zinc acid,
Based on 1 part by weight of the pigment, the amount of addition of taurine and phthalic anhydride as curing assistants was the amount shown in Table 1 with respect to the total amount of the melamine resin molding material. Table 1 shows the change in the post-shrinkage ratio depending on the type and amount of the curing agent and the difference in the mold temperature of the injection molding machine.

[0033]

[Table 1]

As shown in Table 1, according to the present invention, as in Examples 1 to 3, the post-shrinkage rate is smaller than that of Comparative Examples 1 and 2, and is 0.7% or less.

In Examples 4 to 6 and Comparative Examples 3 and 4, a modified melamine resin molding material ME992A60L manufactured by Matsushita Electric Works was used, and a substitute characteristic of warpage due to a difference in mold temperature of an injection molding machine was used. Table 2 shows changes in the orientation difference, bending strength and compressive strength.

In this ME992A60L, phthalic anhydride was used as a curing aid in an amount of 0.22% based on the total amount of the molding material.
It is contained.

[0037]

[Table 2]

As shown in Table 2, according to the present invention, as in Examples 4 to 6, the orientation difference, which is a substitute characteristic of warpage, is smaller than Comparative Examples 3 and 4, and is 0.1% or less. Has become. Further, the bending strength and the compressive strength did not deteriorate, and in Examples 4 to 6, 11 k
gf / mm ² or more and 21 kgf / mm ² or more, which are larger than those of Comparative Examples 3 and 4.

[0039]

According to the method for producing a melamine resin molded article according to the first aspect of the present invention, a melamine resin molded article having low warpage, low post-shrinkage and excellent properties can be obtained.

According to the method for producing a melamine-based resin molded product according to the second aspect of the present invention, a melamine-based resin molded product having further reduced shrinkage and excellent characteristics can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B29C 45 / 00,45 / 72-45 / 73,45 / 78 C08L 61/28

Claims (2)

(57) [Claims] 1. A melamine resin molding material having a mold temperature of 20
A method for producing a melamine-based resin molded product, comprising injection molding at 0 to 250 ° C. 2. The melamine-based resin molding material contains phthalic anhydride in an amount of 0.2 to 0.2% based on the total amount of the melamine-based resin molding material.
The method for producing a melamine-based resin molded product according to claim 1, wherein the content is 0.5% by weight.