JPH0780598A - Water-soluble core material for injection molding - Google Patents

Abstract

PURPOSE: To obtain a core material which is excellent in heat resistance and flow property, and is used in particular for manufacturing a fine injection molded product by using a water soluble high polymer having a hydroxyl group in the core material to be used within a metallic mold for injection molding. CONSTITUTION: The degree of saponification of the core material is suitably controlled to 70 to 95 mol%. The Tg thereof is preferably 00 to 100 deg.C and is measured with a differential thermal scanning calorimeter. Further, the melt index thereof is preferably 0.1 to 50 (210 deg.C and 2160 g load condition as ASTM D-1238). Besides, the water soluble high polymer, suitably the specified amount of oxazoline compound is properly added to improve the flow property and water solubility. Further, for improvement in the flow property, a 0.1-5 pts.wt. polyhydric alcohol compound may be added to the 100 pts.wt. water soluble high polymer. Furthermore, for improvement in the heat resistance, suitably a 1-200 pts.wt. filler having 0.1-200 μm grain size is added to the 100 pts.wt. water soluble high polymer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-soluble core material for injection molding, which is suitable for injection molding, in particular, for fine injection molding and is used in a mold.

[0002]

2. Description of the Related Art US Pat. No. 4,216,257,4290
174, 5040275 discloses an engaging surface fastener member including a base portion, a stem portion, and a Matthew room type head portion, and a manufacturing method thereof. However, these are complicated manufacturing methods, and are not suitable for engaging surface fastener members having a fine pitch and complicated base shape and head shape.

Therefore, a method of manufacturing an engaging surface fastener member by injection molding using a water-soluble core material that can be detached and fractured can be considered. That is, only the stem portion is made using such a water-soluble core material, and the other base portion and head portion are
If it is made by combining permanent molds, it can be applied to the engaging surface fastener member having the above-mentioned fine pitch and complicated base shape and head shape.

Here, the following are known as general water-soluble materials.

1) JP-A-155212 and EP0314
An acrylic polymer material having a carboxyl group, which is disclosed in 156 and is used as a water-soluble core material used in a mold for injection molding.

2) US Patent Nos. 4990146 and 48
The amino group-containing polymer material disclosed in 70148, which is soluble in an acidic solvent or an alkaline solvent.

3) A material comprising an inorganic salt and an inorganic fiber as a water-soluble core material used for die casting, which is disclosed in JP-A-51-50218.

4) A material composed of a water-soluble powder and a ceramic powder, which is disclosed in JP-A-62-255104, as a water-soluble core material used in a mold for injection molding and the like.

5) A filler is added to an acrylic polymer material having a carboxyl group as a water-soluble core material used in a mold for injection molding, which is disclosed in JP-A-1-198609. Material.

However, these materials are heat resistant,
Since it is poor in fluidity and water solubility, such properties are insufficient as a core material for injection molding in general, and particularly for fine injection molding, for example, for producing the above-mentioned engaging surface fastener member.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a core having excellent heat resistance, fluidity and water solubility for injection molding, particularly for producing a fine injection molded article such as an engaging surface fastener member. To provide the material.

[0012]

The present invention relates to a core material used in a mold for injection molding, wherein the core material is
A water-soluble core material for injection molding containing a water-soluble polymer having a hydroxyl group.

In the present invention, the main components of the core material are
The reason for limiting the water-soluble polymer having a hydroxyl group is as follows.

A) The polymer having a hydroxyl group is excellent in water solubility, so that even a finely shaped injection-molded product can be easily produced.
This is because the core dissolves in water or hot water.

B) Since it has a hydrogen bond, it is excellent in thermal stability, and since the high temperature holding time is short even at a melting temperature of the injection molding resin at the time of molding an injection molded product, for example, a temperature exceeding 200 ° C., This is because it is possible to maintain an appropriate shape. In particular, in the case of an injection-molded product having a fine shape, the melting temperature is further increased in order to improve the fluidity of the injection-molding resin, so that the core material preferably has the hydroxyl group of the present invention.

C) On the other hand, at the time of injection molding of the core material itself, the hydroxyl groups are less reactive than other functional groups, for example, carboxyl groups, so that the injection temperature can be increased. As a result, excellent fluidity and thermal stability can be obtained.

D) Furthermore, since water or hot water can be used as the dissolving agent, it is safe and inexpensive.

Specific examples of the water-soluble polymer having a hydroxyl group include polyvinyl alcohol (PVA), hydroxypropyl cellulose, alkyl cellulose, polyvinyl butyral and polyvinyl formal.

Next, the hydroxyl group content will be described.
In the present invention, the hydroxyl group content ratio, for example, the saponification degree is 7
0 to 95 mol% is preferred. It has a hydroxyl group concentration
If it is less than 70 mol%, it is difficult to obtain excellent water solubility, while
This is because when the hydroxyl group concentration exceeds 95 mol%, the hydroxyl groups react with each other at around 240 ° C. to cause dehydration and cross-linking reaction, resulting in a significant decrease in water solubility.

The functional group contained in the water-soluble polymer of the present invention is preferably a hydroxyl group.
It is possible to have other functional groups such as a carboxyl group and an amino group together with the hydroxyl group within the range not deviating from the purpose, the effect and the like.

The core material of the present invention has a Tg of 40 to 1.
It is preferably 00 ° C. This is because if the Tg is less than 40 ° C., the heat resistance becomes poor and it becomes difficult to use it as a core material used in a mold for injection molding. On the other hand, if the Tg exceeds 100 ° C., it becomes difficult to injection-mold the core itself, and the water solubility decreases, and it becomes difficult to use it particularly in an injection-molded product having a fine shape. The Tg can be measured with a differential scanning calorimeter (DSC).

The core material of the present invention has a melt index (MI) of 0.1 to 50 (ASTM D-.
1238-based 210 ° C., 2160 g load condition) is preferable. This is because if the MI is less than 0.1, the fluidity becomes poor, and it becomes difficult to use it particularly as a core material for an injection molded product having a fine shape. On the other hand, MI
Is more than 50, the average molecular weight of the core material becomes relatively low and the heat resistance becomes poor.

The core material of the present invention may appropriately contain an oxazoline compound in addition to the above water-soluble polymer. The oxazoline compound is defined as a molecular material having an oxazoline skeleton in the molecule, and for example, 2-vinyl-2-oxazoline, 5-methyl-2-vinyl-2-oxazoline, 4,4-dimethyl-2-vinyl. 2-oxazoline, 4,4-dimethyl-2-vinyl-5,6-dihydro-4H-1,3-oxazine, 4,4,6-trimethyl-2-vinyl-5,6-dihydro-4H-1 , 3
-Oxazines or their polymers such as poly (2-
Ethyl-2-oxazoline) and the like can be used.

The reason why it is preferable to add the oxazoline compound is that the fluidity and water solubility can be improved while maintaining the heat resistance of the core resin. The addition amount of the oxazoline compound is preferably 5 to 30 parts by weight with respect to 100 parts by weight of the water-soluble polymer having a hydroxyl group. This is because if the addition amount of the oxazoline compound is less than 5 parts by weight, the improving effect of the oxazoline compound will be poor, and if the addition amount exceeds 30 parts by weight, the heat resistance may decrease.

Next, the core material of the present invention may contain a polyhydric alcohol compound. The polyhydric alcohol compound, by adding a small amount, remarkably improves the fluidity of the core resin, and also has an intramolecular hydrogen bond because it has a plurality of hydroxyl groups in the molecule, and therefore has a relatively high boiling point. Even when used in the mold of the present invention, there are few problems such as foaming and bleeding, which is preferable. In addition, when the core material of the present invention contains an inorganic substance, a metal oxide filler, or the like, the polyhydric alcohol compound is also preferable from the viewpoint of improving the dispersibility of the filler.

Here, the polyhydric alcohol compound is defined as a compound having two or more hydroxyl groups in at least the molecule, and examples thereof include glycerin, ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol and hexa. Methylene glycol,
Propylene glycol, 2,3-butanediol, 1,
3-Butanediol, diethylene glycol, triethylene glycol, lecithin and the like can be used. The addition amount of the polyhydric alcohol compound is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the water-soluble polymer having a hydroxyl group. The amount of polyhydric alcohol compound added is 0.1
If it is less than 10 parts by weight, the improving effect of the polyhydric alcohol compound is poor, while if it is more than 10 parts by weight, the Tg of the water-soluble polymer and the Tg of the core material may be extremely lowered. Is.

The core material of the present invention may contain a filler, which improves the heat resistance of the core material,
The mechanical strength of the core material is improved, increasing the amount (cost is low)
Therefore, the fluidity of the core material during injection molding is improved, the solubility of the core material in water is improved, the surface of the injection molded product becomes smooth, and the storage stability of the core material is improved.

As the filler, talc, glass beads, hollow glass beads, silica particles, alumina oxide,
Calcium carbonate, titanium oxide, magnesium oxide, zinc oxide, zirconia oxide, aluminosilicate, mica,
Barium sulfate, calcium phosphate, kaolin, zeolite, iron, titanium, nickel, copper, magnesium, tin,
Lead, zinc, metal salts, crosslinked silicone resin, etc. may be used.

The amount of the filler added is 1 to 200 with respect to 100 parts by weight of the water-soluble polymer having a hydroxyl group.
Weight parts are preferred. If it is less than 1 part by weight, the improvement effect is poor. If the amount exceeds 200 parts by weight, the moldability of the core becomes poor and the injection molding machine may be worn.

The filler preferably has an average particle size measured by an image processing device of 0.1 to 600 μm,
Particularly preferably, it is 1 to 200 μm. If it is less than 0.1 μm, the improvement effect due to the addition of the filler is poor, and it is difficult to disperse the filler in the polymer. 600 μm
If it exceeds, the surface smoothness of the injection molded product becomes poor. Even when applied to a finely shaped injection-molded product, if the particle size is 600 μm or less, the particle size can be adjusted by appropriately pulverizing it when dispersing it in a polymer with a screw or the like. Therefore, it can be used in the present invention. Furthermore, 1-2
Within the range of 00 μm, there is little risk of wear of the injection molding machine, it is easy to separate from the polymer product, waste liquid treatment is easy, and it is easy to apply to injection molded products of fine shape.

The specific gravity of the filler is preferably 1.05 or more or 0.95 or less. If 1.05 or more,
This is because when the water-soluble core is dissolved, the particles are likely to settle, and the water-soluble core can be dissolved more easily by using a centrifuge. Further, a more preferable specific gravity is
It is 1.3 or more. This is because it is easy to separate and collect the particles from the water-soluble core. On the other hand, when the specific gravity is 0.95 or less, the particles float on the water surface when the water-soluble core is dissolved, so that separation and reuse of the particles are extremely easy.

The shape of the filler is preferably spherical and has a uniform particle size distribution. This is because the filling rate in the resin can be made extremely high as compared with the case where the shape is irregular. Even if a large amount is added, if the resin has a uniform spherical shape, the fluidity of the core resin is hardly affected when the core resin is injection-molded. Furthermore, the mechanical strength of the filler itself is high, so that it can be reused, the cost is low, and because it is easy to arrange the filler evenly on the core surface, the resulting injection molded product has high surface smoothness and reproducibility. There is also an advantage.

In order to improve the compatibility with the core material, it is also preferable to surface-treat the above-mentioned filler with a silane coupling agent and / or a titanium coupling agent.

The core material of the present invention may contain a pigment or a dye. In the water-soluble process of the core material, the concentration of the core material in water has a strong influence on the dissolution rate of the core material, and therefore the management of the aqueous solution is important. Therefore, such control can be performed very easily by visual inspection using a pigment or dye that dissolves in water together with the core. Furthermore, by using a pigment or dye having a color different from that of the injection-molded product, it becomes possible to very easily visually judge the insufficient solubility of the core material. On the other hand, if a pigment or dye having a color similar to that of the injection-molded product is used, the appearance may be impaired even if the core material is slightly attached to the range of the function of the injection-molded product. Less is.

The type of the pigment or dye is not particularly limited. It is possible to use organic pigments and organic dyes such as azo dyes, nitroso dyes, anthraquinone dyes, indigo dyes, sulfur dyes, basic dyes, acid dyes, thiazole dyes, and naphthol dyes.

The amount of the pigment or dye added can be determined by judging from chromaticity, brightness, saturation and the like. Specifically, 0.01 to 5 parts by weight is suitable for 100 parts by weight of the water-soluble polymer having a hydroxyl group. If it is less than 0.01 part by weight, the coloring effect is generally poor. Also, if the amount exceeds 5 parts by weight, it becomes difficult to control the aqueous solution in the water-soluble step of the core material.

The core of the present invention may contain carbon black. Thereby, the heat resistance and the reinforcing effect of the core material can be improved. Since the particle size of carbon black is relatively small, the surface smoothness of the injection molded product is improved. In addition, carbon black has excellent hiding power, and blackening of the core material can be achieved with a small amount of addition. On the other hand, if the color of the injection-molded product is black, the injection-molded product can be injection-molded within the range not impairing its function. Even if the core material is slightly attached to the product, there is little risk of impairing the appearance. It becomes possible to easily control the aqueous solution by visual inspection or the like by using the carbon black that flows out together with the core. Further, since carbon black is low in cost, it has an effect of increasing the amount.

The type of carbon black is not particularly limited. As a specific example, Channel Black,
Thermal black, furnace black, etc. can be used.

The amount of carbon black added can be determined by judging from the degree of blackness and the like. Specifically, it is 0.05 to 100 parts by weight of the water-soluble polymer having a hydroxyl group.
20 parts by weight is preferred. If it is less than 0.05 parts by weight, the improvement effect is generally poor. Also, if it exceeds 20 parts by weight,
This is because it is rather difficult to control the aqueous solution of the core material in the water-soluble process.

[0040]

EXAMPLES The present invention will now be described in more detail based on examples.

(Examples 1 to 8 and Comparative Example 1) As shown in Table 1,
Polyvinyl alcohol manufactured by Nippon Synthetic Chemical Co., Ltd. or acrylic water-soluble resin manufactured by Belant Co., Ltd. was dried for 24 hours or more using a hot air dryer whose temperature was controlled at 50 ° C., and then a molding machine manufactured by Nissei Plastic Industry Co., Ltd. With PS-40 type, 210 ° C or 22 using core type No. 6 manufactured by Sumitomo 3M Limited
The core was molded at 5 ° C. Then, using this core, a standard surface fastener made of M4745 polypropylene resin manufactured by Asahi Kasei Co., Ltd. was created by the molding machine PS-40 type manufactured by NISSEI PLASTIC INDUSTRIAL CO., LTD., And the following evaluation was performed. The results are shown in Table 1.

1) Measurement of Tg of core material Using DSC-2C manufactured by Perkin Elmer, the temperature was raised from -60 ° C to 300 ° C under the condition of 10 ° C / min, and the change point of the specific heat in the dynamic mode. Was measured and defined as Tg.

2) Measurement of MI value of core material ASTM D-1238 (210 ° C., load 2160 g)
In accordance with, the MI value of the core material was measured using Toyo Seiki Melt Indexer S-101.

3) Measurement of core filling ratio (actual core resin weight / theoretical core resin weight) The core resin is actually 210 ° C. or the theoretical core resin weight determined from the core type volume. The core filling rate was defined as the weight ratio of the core material obtained by injection molding at 225 ° C.

4) Solubility Evaluation The resulting core material was dipped in water or hot water at 23 ° C. or 70 ° C. for 24 hours, and the solubility of the core material was visually evaluated according to the following criteria. OK: completely dissolved. FAIR: Almost dissolved. NG: Some remain.

5) Evaluation of Appearance of Engagement Surface Fastener Member The appearance of the completed engagement surface fastener member was judged according to the following criteria. OK: No problem NG: Some problems

[Table 1] Examples Comparative Examples 1 2 3 4 5 6 7 8 1 GBC PVA, etc. (* 1) KP06 KL05 KM11 GL03 GL05 GM14 GH23 NL05 1330TE Degree of saponification 71 80 78 87 88 90 87 99 < -Tg / ℃ 57.0 73.4 75.0 69.4 68.0 74.5 72.0 80 − MI 4.0 3.3 2.6 4.5 3.1 0.3 0.1 2.0 8.2 Filling rate 210 ℃ 100 100 95 100 100 80 65 100 100 225 ℃ 100 100 100 100 100 100 100 100 100 Solubility 25 ℃ OK OK OK OK OK OK OK NG NG 70 ℃ OK OK OK OK OK OK OK OK OK FAIR Appearance OK OK OK OK OK OK OK OK NG * 1) KP06, KL05, KM11, GL03, G
L05, GM14, GH23 and NL05 are trade names of polyvinyl alcohol of Nippon Synthetic Chemical Industry Co., Ltd. GBC
1330TE is a brand name of acrylic water-soluble resin manufactured by Belant.

(Examples 9 to 13 and Comparative Example 2) As shown in Table 2, polyvinyl alcohol manufactured by Nippon Synthetic Chemical Industry Co., Ltd. was dried for 24 hours using a hot air dryer whose temperature was controlled at 50 ° C. A polyhydric alcohol, an oxazoline compound, carbon black and a filler were added and sufficiently mixed to obtain a core material. Then, a standard surface fastener was manufactured in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 2. The number after the component code of the core material represents the blending amount (% by weight).

[0049] Table 2 Example Comparative Example 9 10 11 12 13 2 core material GL03 / 75 KL05 / 85 GL05 / 79 GL03 / 99 GL03 / 40 GL03 / 80 (* 2) GRI / 3 GRI / 0.1 GRI / 17.5 PEOX / 15 PEOX / 2 CB / 1 AO-502 / 22 Talc / 20 ML3050 / 1 SO-C5 / 60 Talc / 0.5 Tg / ℃ 54 68 67 69 69 32 MI 8.4 3.8 3.6 3.7 4.5 60 Saponification degree 87 80 88 87 87 87 Filling rate 210 ℃ 100 100 100 100 100 103 225 ℃ 100 100 100 100 100 104 Solubility 25 ℃ OK OK OK OK OK OK 70 ℃ OK OK OK OK OK OK Appearance OK OK OK OK OK OK NG * 2) GRI = glycerin. Made by Wako Pure Chemical Industries, Ltd. PEOX = trademark of polyethyloxazoline manufactured by Dow Chemical Company. C. B. = Carbon black manufactured by Asahi Carbon Co., Ltd., Asahi Carbon Black (trademark). Average particle size (measured by an electron microscope or an image processing device; the same applies hereinafter) 80 μm AO-502 = alumina spherical powder manufactured by Admatechs Co., Ltd., trade name of Admuffin ™. Average particle size 0.1
0.7 μm. Specific gravity 3.6. Talc = manufactured by Nippon Talc Co., Ltd. Scale-like, grain size 7.0μ
m. Specific gravity 2.7. ML3050 = trade name of Macrolite (trademark), spherical particles of alumina silicate manufactured by 3M Company, USA. Average particle size 300 ~
600 μm. Specific gravity 1.05. SO-C5 = silica spherical powder manufactured by Admatechs Co., Ltd.,
Product name of Admuffin (trademark). Average particle size 1.5-2
μ. Specific gravity 2.21.

(Examples 14 to 17) As shown in Table 3,
After drying polyvinyl alcohol manufactured by Nippon Synthetic Chemical Industry Co., Ltd. for 24 hours using a hot air dryer whose temperature is controlled at 50 ° C., the filler type, particle size, and specific gravity are changed, and this is added and thoroughly mixed. A core surface material was used, and then a standard surface fastener was manufactured in the same manner as in Example 1, and the same evaluation as in Example 1 was performed. The results are shown in Table 3.

[Table 3] Example 14 15 16 17 FILER GL03 / 80 GL03 / 80 GL03 / 80 GL03 / 80 / PHR 20 20 20 20 types (* 3) GB731 SO-C2 ML3050 C-15 / 250 Average particle size (Μm) 30 0.5 300-600 66 Specific gravity 2.5 2.2 1.05 0.15 Tg / ℃ 69 69 68 68 MI 6.1 5.3 2.8 1.9 Filling rate 210 ℃ 100 100 100 100 225 ℃ 100 100 100 100 Solubility 25 ℃ OK OK OK OK 70 ℃ OK OK OK OK Appearance OK OK OK OK * 3) GB731 = Trade name of glass beads manufactured by Toshiba Baronitini Co., Ltd. SO-C2 = spherical silica powder manufactured by Admatechs Co., Ltd.,
Product name of Admuffin (trademark). C15 / 250 = trade name of Scotchlight Glass Bulbs (trademark), a glass balloon manufactured by 3M Company of the United States.

[0052]

According to the present invention, there is provided a core material having excellent heat resistance and fluidity for injection molding, particularly for producing a fine injection molded article such as a fastener member.

Continuation of front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location B29C 45/26 7158-4F (72) Inventor Shinji Torigoe 3-8-8 Minamihashimoto, Sagamihara-shi, Kanagawa Sumitomo 3M Stock In the company

Claims (13)

[Claims] 1. A water-soluble core material for injection molding, which comprises a water-soluble polymer having a hydroxyl group in a core material used in a mold for injection molding. 2. The water-soluble polymer has a saponification degree of 70 to 95.
The water-soluble core material for injection molding according to claim 1, wherein the water-soluble polymer is mol%. 3. The water-soluble core material for injection molding according to claim 1, wherein the Tg of the core material is 40 to 100 ° C. 4. The melt index of the core material is:
0.1-50 (210 ° C according to ASTM D-1238,
The water-soluble core material for injection molding according to claim 1, 2 or 3, which is 2160 g load condition). 5. The water-soluble core material for injection molding according to claim 1, wherein the core material contains an oxazoline compound. 6. The core material is the water-soluble polymer 10.
0.1 to 5 parts by weight of polyhydric alcohol compound relative to 0 parts by weight.
The water-soluble core material for injection molding according to any one of claims 1 to 5, wherein the water-soluble core material comprises parts by weight. 7. The core material contains a filler,
The water-soluble core material for injection molding according to any one of claims 1 to 6. 8. The core material is the water-soluble polymer 10.
The water-soluble core material for injection molding according to claim 7, which contains 1 to 200 parts by weight of the filler with respect to 0 parts by weight. 9. The particle size of the filler is 0.1 to 200 μm.
The water-soluble core material for injection molding according to claim 7 or 8, which is m. 10. The water-soluble core material for injection molding according to claim 7, 8 or 9, wherein the specific gravity of the filler is 1.05 or more. 11. The water-soluble core material for injection molding according to claim 7, 8 or 9, wherein the specific gravity of the filler is 0.95 or less. 12. The water-soluble core material for injection molding according to claim 1, wherein the core material contains a pigment or a dye. 13. The water-soluble core material for injection molding according to claim 1, wherein the core material contains carbon black.