MXPA96004403A - Nucleus material and process for molding by inyecc - Google Patents

Abstract

A core material for injection molding, comprising a copolymer of a polyvinyl alcohol (PVA) and polyethylene oxide (PEO), as well as a core formed from the core material.

Description

NUCLEUS MATERIAL AND PROCESS FOR 'MOLDING BY INJECTION FIELD OF THE INVENTION The present invention relates to a core material composed of a water-soluble material. The core material of the present invention is useful especially for the preparation of a core for injection molding plastic products or parts with a fine structure, for example, a front fastener (Hook and Ring Holder) used in the field of automotive industry, and so on.

BACKGROUND OF THE INVENTION For the material for the preparation of a core for the injection molding of products or parts of high molecular weight material with a fine structure, it is necessary to satisfy the conditions that it is easy to mold a core having a fine structure itself, and that after the products or parts of high molecular weight material have been molded, the used core can easily dissolve in water and be eliminated. REF: 23107"" "The North American Patent No. 5,242,646 describes a process for the production of a front fastener composed of a head, spigot and base portion, and in this process, PVA is used as a core material However, since PVA melts and decomposes (thermal crosslinking) simultaneously, there have been difficulties with the formation of a core itself As a water-soluble core material for the injection molding of a high molecular weight material , a high molecular weight acrylic material having a carboxyl group in the Publication of Unexamined Japanese Patent No. 60-155212 and EP 0314156.

In the North American Patent No. 4,990,146 and the Patent No. 4,870,148, high molecular weight materials containing an a-ino group, soluble in an acid solvent or alkaline solvent, were described. Also, in the Unexamined Japanese Patent Publication No. 1-198609, a material obtained by the addition of a filler to a high molecular weight, acrylic material containing a carboxyl group was described as a water-soluble core material. However, those water-soluble materials have had the defect of having insufficient thermal resistance and fluidity, in the formation of a core, or have had the disadvantage that they are poorly soluble in water in the case where the core used will be eliminated by the use of water.

BRIEF DESCRIPTION OF THE INVENTION Therefore, the present invention relates to a core material for injection molding, and the purpose of the present invention is to provide a core material, which has sufficient thermal resistance and fluidity to form a core, thus facilitating both the precise formation of a core that has a small structure, and that dissolves easily in water in the event that the used core dissolves in water and is eliminated. The present inventors studied several ways to solve the aforementioned problem, and subsequently found that a composition comprising a polyvinyl alcohol (PVA) and polyethylene oxide (PEO) meet the requirements mentioned above, to achieve the present invention. Accordingly, the present invention provides a core material for injection molding, comprising a copolymer of a polyvinyl alcohol (PVA) and .. polyethylene oxide (PEO), and the use thereof.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES In the present invention, a copolymer of a polyvinyl alcohol (PVA) and polyethylene oxide (PEO) was used as the water-soluble core material to be used in a mold for injection molding or the like. A polyvinyl alcohol (PVA) has a melting point that fluctuates from 170 ° C to 230 ° C according to different degrees of saponification. However, any PVA begins to decompose thermally at a temperature exceeding 200 ° C, and at a temperature of 240 ° C or more, the dehydration and crosslinking reaction of the PVA proceeds, and therefore, the PVA has the defect that the water solubility thereof decreases markedly. As described above, in the case of the thermal work of the PVA, since the decomposition reaction of the PVA occurs parallel to the thermal work of the PVA, the thermal work of the PVA has been very difficult. On the other hand, it is also known that polyethylene oxide (PEO) is a water soluble resin. However, the PEO is of very poor fluidity when injected, compared to a PVA that has a molecular weight of the same degree as that of the PEO, and is therefore unsuitable for the production of an injection molded product in the same way as the PEO. fine. The copolymer of a polyvinyl alcohol (PVA) and polyethylene oxide (PEO) is capable of relatively lowering the hydroxyl group concentration that causes the chemical reaction. Although its high solubility in water is maintained, because the copolymer has a hydroxyl group and an ether bond in the structure thereof, and therefore, the copolymer is more stable than. a PVA. In addition, the introduction of an ether bond gives a low melting point to the copolymer, and therefore, can solve the problem related to the thermal workability of the PVA. The portion of the PVA constituting the above copolymer includes the range of a plurality of saponified PVA having a completely saponified PVA acetic group, according to the degree of saponification. The molar ratio between the PVA and the PEO in the copolymer mentioned above is preferably within the range of 99 to 50 (PVA): 1 to 50 (PEO). Within this range of ratio, sufficient thermal stability and sufficient fluidity can be obtained at the time of forming a core, as well as a sufficient water solubility of the core used, but, when the proportional amount exceeds 50%, the viscosity of the core becomes so high that it becomes difficult to form a core having a fine shape. On the other hand, when the proportional amount is less than 1%, the thermal stability of the core material is so low that thermal crosslinking occurs due to heating during core formation, and the water solubility of the core used is likely to decrease. The molar ratio between the PVA and the PEO in the polymer is more preferably within the range of 95 to 55 (PVA): 5 to 45 (PEO). Within this range, the features mentioned above are emphasized to a greater degree. The molar ratio between the PVA and the PEO in the polymer is still more preferably within the range of 90 to 70 (PVA): 30 to 10 (PEO). Within this range, the features mentioned above are emphasized to an even greater degree. The degree of saponification of PVA is preferably 65 mol% or more, for example, within the range of between 65 and 99 mol%. Here, the degree of saponification of 99 mol% means the maximum value of the degree of saponification actually available. When the degree of saponification is less than 65 mol, the PVA exhibits high hydrophobicity, and the solubility of the PVA in water is susceptible to lowering. The degree of saponification of the PVA is more preferably 70 mol% or more, for example, within the range of 70 and 99 mol% When the degree of saponification is 70 mol% or more, especially the solubility in PVA water becomes high The degree of saponification of the PVA remains, more preferably of 80 mol%, or more, for example, within the range of between 80 and 99 mol% When the degree of saponification is 80 mol% or more, the melting point of the PVA is increased, while the solubility in water thereof is conserved, and the thermal resistance of the PVA is improved in the case of parts or the like which are injection molded. of the water-soluble core material of the present invention is one having a Tq value that ranges from 40 ° C to 100 ° C. Because, when the value of Tg is less than 40 ° C, the material of the core is poor in its thermal resistance, and inadequate as core material for to be used in a-mold for injection molding. On the other hand, when the value of Tq exceeds 100 ° C, the injection molding of the core itself becomes difficult, and in addition, the water solubility of the core material decreases. Therefore, it becomes difficult to use the core material, especially for an injection molded product having a fine shape. The preferred embodiment of the water-soluble core material of the present invention includes a water-soluble high molecular weight material, in which the MI value of the aforementioned water-soluble core material is within the range of 0.1 and 50 ( according to ASTM D-1238, at 210 ° C, under a load of 2160 g). The reason why the value of MI is limited within the range of 0.1 and 50 in the present invention is that when the value of MI is less than 0.1, the fluidity of the core material becomes poor in a mold for molding by injection, resulting in the difficulty of using the core material, especially for an injection molded product having a fine shape, and on the other hand, when the MI value exceeds 50, the average molecular weight of the core material is becomes relatively low, resulting in a decrease in the thermal resistance of the core material. As the commercially available concrete PVA / PEO polymer, there may be mentioned the copolymers of PVA / PEO soluble in water, "Ax 300", "Ax 2000", and the like produced by Nihon Gosei Kagaku Kogyo K.K. (Japan Synthetic Chemistry Ind. Co., Ltd.). To obtain the water-soluble core material of the present invention, an oxazoline compound, polyethylene oxide (PEO), and / or PVA can be added to the aforementioned core material. An oxazoline compound is defined as a high molecular weight material that has a • oxazoline skeleton in the molecule, and as an oxazoline compound, for example poly (2-ethyl-2-yl) oxazoline and the like can be used, the reason why an oxazoline, PEO or PVA compound is added it is here that it makes it possible to improve the fluidity and water solubility of the core material if it damages the thermal resistance thereof, especially as PVA, one having a hydroxyl group concentration ranging from 70 to 95 mol% is preferred. this is that, when the concentration of the hydroxyl group is less than 70 mol%, the solubility in water of the PVA decreases, on the one hand, and on the other side, when the concentration of the hydroxyl group exceeds 95 mol%, not only the solubility in water of low PVA, but also the thermal resistance thereof is markedly damaged. The proportional amount of oxazoline compound, POE or POE to be added is preferably within the range of between 5 and 60 parts by weight on 100 parts by weight of the present water-soluble copolymer. Because when the amount of the added oxazoline compound, PEO or PVA is less than 5 parts by weight, the favorable effect that is expected to be obtained by the addition of those substances is poor, and on the other hand when this amount exceeds 60 parts by weight, the thermal resistance of the core material becomes noticeably less so that the PVA becomes unsuitable for the production of an injection molded product having a fine shape. To the water-soluble core material of the present invention, a polyhydric alcohol compound, filler, pigment and / or dye may also be added. The addition of a small amount of a polyhydric alcohol compound can improve the flowability of the core resin. Furthermore, since a polyhydric alcohol compound has a hydroxyl group in the molecule, at the boiling point thereof, it is relatively high, and also in the use thereof in a mold of the. present invention, did not cause problems such as foaming and runoff. In addition, the polyhydric alcohol compound is more effective also because it improves the dispersibility of fillers such as inorganic matter or metal oxides and coloring pigments. A polyhydric alcohol is defined as a compound having at least two hydroxyl groups to the molecule, and as a polyvalent alcohol, there may be used, for example glycerin, ethylene glycol, trimethylene glycol, tetramethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, 2, 3-butanediol, 1,3-butanediol, pentamethylene glycol, and the like. The fillers are effective for improving thermal resistance, mechanical strength, weight effect "" (reduction of cost fluidity, and Solubility of the core material of the present invention, and as fillers, for example, talc, pearls of glass, hollow glass beads, magnesium carbonate, mica, aluminum silicate, calcium phosphate, zeolite, metal salts, as well as metal oxides such as titanium, tin, magnesium and zinc The amount of fillers to be added is preferably within the range of 1 and 50 parts by weight based on 100 parts by weight of the water-soluble core material mentioned above, in general, although not particularly limited Within a range other than the range mentioned above, the fillers They are poor in the favorable effects mentioned above.It is also favorable to praise the compatibility of fillers such as glass beads on the core material by subjecting them to a coupling treatment. The pigments or dyes are very effective in recognizing the dissolved state of the core material of the present invention, and in turn, adhesion of the core material to an injection molded product such as a front fastener, by visual observation or the like. For example, by using a core color different from the color of the injection molded product, the adhesion of the core material to the product can be easily recognized. Although the types of pigments or dyes to be used are not particularly limited, they can be used, as pigments or dyes, carbon black, organic pigments, titanium white, and organic dyes such as azo dyes, acid dyes, basic dyes, dyes of thiazole, and naphthol stains. The amount of pigments or dyes to be * added is preferably within the range of 0.01 to 5 parts by weight, based on 100 parts by weight of the water-soluble core material. When this amount is less than 0.01 parts by weight, the recognition effect mentioned above becomes poor, and on the other hand, when it exceeds 5 parts by weight, on the contrary, the pigments or dyes adhere to the injection molded product, and it takes time and work to eliminate them, on the contrary. According to the present invention, there is provided a process for the production of a core characterized by the function of the present core material at a temperature of at least 50 ° C, and the injection molding of such a core material in a mold. Here, the reason why the core material is heated to at least 150 ° C is because by this method a lower melt viscosity can be obtained, and an injection molded article such as a front fastener part having a base portion and a plurality of regularly positioned projections having a projection or leg generated from the base portion and a fungus-shaped head connected to the end of the leg can be produced with high accuracy in a short time. As heating means, a heater, infrared light, etc. can be used. As the melting temperature, 160-260 ° C, 190-240 ° C is preferable. In the first range, a lower melt viscosity and a non-crosslinked core material are obtained by overheating In the last range, a lower melting temperature is obtained, and a non-crosslinked core material is obtained. In the production of a core, a molten core material is preferably molded into a desired shape in the mold.Small-shaped articles can easily be produced in a short time.Note that to accelerate the solidification of a core and to removing the core at the beginning and in a short time, the mold is preferably cooled to a predetermined temperature with, for example, cold air As can be seen from the above, by using the present core material, the core soluble in water for injection molding, which is "" "excellent in heat resistance, fluidity and water solubility. Further, after that, while maintaining the core in the same "mold, a molten material for injection molding can be injection molded.As a result, an article of fine and complicated shape such as a part of surface fastener can be molded in a single step Note that, when the molten material for the injection molded articles is injected, to preserve the shape of the core, the injection is desirably carried out at a temperature lower than the melting temperature of the core. Note that a process for forming a core and a process for the production of an article formed using the core is described in detail in U.S. Patent No. 5,242,646 In the following, the present invention will be explained in more detail with reference to the working examples and comparative examples.

Table 1 Ax300: Water soluble PVA / PEO copolymer resin, "ECOMATY" produced by Japan Synthetic Chemistry Ind. Co., Ltd. Ax2000: Copolymer resin of PVA / PEO sol_jole in water, "ECOMATY" produced by Japan Synthetic Chemistry Ind. Co., Ltd. AL03-2: Polyvinyl alcohol produced by Japan Synthetic Chemistry Ind. Co., Ltd. GL05: Polyvinyl alcohol produced by Japa Synthetic Chemistry Ind. Co., Ltd. KP08: Polyvinyl alcohol produced by Japan Synthetic Chemistry Ind. Co., Ltd. KL05: Polyvinyl alcohol produced by Japan Synthetic Chemistry Ind. Co., Ltd. GBI330TE: Water-soluble acrylic resin produced by Berrant Co., Ltd. PEOX200: Poly (ethyl oxazoline) produced by Dow Chemical Co. ., Ltd. PEO-1: Poly (ethylene oxide) produced by Sumitomo Seika Co., Ltd. GB731B: Glass beads produced by Toshiba Barotini Co., Ltd. Talcum: "Talc MS-A11 produced by Japan Tale Co., Ltd. Coal:" Asahi Thermal "produced by Asahi Coal Co., Ltd.

Table 2 Elos 1 and 2 and Comparative Examples 1 to 3 The water soluble resin, "ECOMATY" produced by Nihon Gosei Kagaku Kogyo K.K. (Japan Synthetic Chemistry Ind. Co., Ltd.) and a PVA were dried for 24 hours by using a hot air dryer, subsequently a core was produced at a temperature of 210 ° C by using a core mold No. 6 produced by Sumitomo 3M Co., Ltd. by an injection molding machine of the "PS-40" type produced by Nissei Jushi Kogyo KK [Nissei Resin Ind. Co., Ltd.]. Subsequently, by using the core thus produced, it was produced with the aforementioned injection molding machine of the type "PS-40" produced by Nissei Jushi Kogyo K.K., a standard front fastener, a product of Su itomo 3M Co. , Ltd., and underwent the following evaluations. 1. Determination of the Degree of Saponification: The degree of saponification will be calculated from the integrated intensity ratio determined by the use of a nuclear magnetic resonance device "EX 270", produced by Nihon Denshi K.K. [Japan Electronic Co., Ltd.] 2. Determination of the Melting Point (Tm) and the Vitrea Transition Temperature (Tq) of the Core Material. The temperature of the core material was raised from -60 to 300 ° C at a rate of 10 ° C / min by using a "DSC-2C" manufactured by Perkin Elmer Ind. Co., Ltd., and the values of Tm and Tq were determined from the change of the specific heats. 3. Determination of the Decomposition Temperature (Td) of the Core Material: The temperature of the core material was raised at a speed of 10 ° C / min by the use of an apparatus for thermogravimetry "951" manufactured by DuPont Co., Ltd. , and the temperature of decomposition to atmospheric air was determined. 4. Determination of the Melt Index (MI) of the Core Material: The values of the melt index (MI) of the core materials were determined, respectively, by the use of a device to determine the r index of Fusion s-1001 manufactured by Toyo Seiki Ind. Co., Ltd., according to ASTM D-1238 (at 210 ° C, under a load of 2160g).

. Solubility Evaluation: Non-dissolved products in which a front fastener material (1011CH5) is integrated with a core were immersed in water at 23 ° C or hot water at 70 ° C for 24 hours. Subsequently, the solubility of each core material was judged visually according to the following criteria, OK: completely dissolved. ' Almost: Almost completely dissolved, NG: Partially undissolved. 6. Thermal Resistance Evaluation: Using the high molecular weight materials described below as members of the fastener, the front fasteners were prepared under the temperature conditions described below, respectively. Subsequently, a bar was cut. linear of each frontal fastener in the longitudinal direction, and the thermal resistances of the core materials were evaluated microscopically judging the shape and uniformity of the group of bars observed from the direction of the cross section of the linear bar, according to the following criteria .

Polypropylene "6800i" manufactured by Mitsubishi 210 ° C Chemical Ind. Co., Ltd. 6-nylon "1011CH5" manufactured by Mitsubishi Chemical 250 ° C Ind. Co., Ltd. 6, 6-nylon "1200S" manufactured by Asahi Chemical Ind. 280 ° C Co. , Ltd. OK: No problem NG: Partially objectionable The results are shown in Table 3.

Table 3 • Example 1 Example 2 Ex. Comp. 1 Ex. Comp.2 Ex. Comp. 3 Water Soluble Resin. »X300 Ax2000 G 05 K 05 1330TE [parts by weight] (100) (100) (100) (100) (100) T, [° C] 54 50 68 61 102 MI (210CC, 2160g) 2.9 21.8 2.4 6.4 12.5 Solubility 23 ° C OK OK NG Almost NG 70 ° C OK OK Almost OK Almost Thermal Resistance \ 6T00J OK OK OK OK OK. 1011CH5 OK OK NG NG NG 1200S OK OK NG NG NG Examples 3 to 7 and Comparative Examples 4 and 5 The water soluble resin "ECOMATY" and the PVA produced by Japan Synthetic Chemistry Co., Ltd. were dried for 24 hours or more by the use of a hot air dryer, the temperature of which had been controlled at 50 ° C, after which a polyhydric alcohol, oxazoline compound, carbon black, and fillers were added, until sufficiently mixed so that the core materials are prepared. Subsequently, the core materials thus prepared were evaluated with respect to the following points as in Example 1 mentioned above. 1. Determination of the melting indices (MI) of the core materials 2. Evaluation of the solubility 3. Evaluation of the thermal resistance The results are shown in Table 4.

Table 4 Example 3 Example 4 Example 5 Example 6 Example 7 Ex. Comp. 4 Ex Comp. 5 Water Soluble Resin Ax300 Ax200 Ax300 Ax2000 Ax2000 KL05 Ax2000 (100) (100) (100) (100) (100) (100) (100) Other Resins KP08 PEOX200 PEO-1 PBOX50 (50) (30) (10) (70) Polyhydric alcohols glycerin glycerin glycerin glycerin (2) (1) (1) (2) Talc fillers GB731B talc talcum powder NJ (15) (40) (30) (30) Pigment or Charcoal Dye (1) - • Fusion index (210 ° C, 2160g) 0.2 45.1 1.3 18.5 14.2 3.1 54.4 Solubility 23 ° C OK OK OK OK NG OK 70 ° C OK OK OK OK OK Almost OK Thermal resistance 6800J OK OK OK. or? OK OK NG 1011CH5 OK OK OK or? - OK OK NG 1200S OK OK OK OK OK NG NG As mentioned in detail above, according to the present invention, by the use of PVA and PEO, a core having a fine form of glass * can be easily prepared to excellent thermal stability and fluidity, and the core used can be easily dissolved and eliminated by the use of water. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following:

Claims (10)

..CLAIMS

1. A core material for injection molding, characterized in that it comprises a copolymer of polyvinyl alcohol (PVA) and polyethylene oxide (PEO).

2. The core material according to claim 1, characterized in that a molar ratio between the PVA and the PEO of the copolymer is within a range of between 99: 1 and 50:50.

3. The core material according to claim 1, characterized in that the degree of saponification of the PVA is within a range of between 65 and 99 mol%.

4. The core material according to claim 1, characterized in that the glass transition temperature (Tg) of the core material is within the range of 40C, C and 100 ° C.

5. The core material according to claim 1, characterized in that the melt index (MI) of the core material is within a range of 0.1 and 50.

6. The core material according to claim 1, characterized in that it further comprises an oxazoline compound, PVA and / or PEO.

7. A process for the production of a core, characterized by the melting of a core material according to claim 1, at a temperature of at least 150 ° C, and the injection molding of such molten core material in a mold.

8. An injection molded article, characterized in that it is formed using a core according to claim 7.

9. An injection molded article, according to claim 8, characterized in that it is a front fastener.

10. A process for the production of an injection molding article characterized in that it positions a core according to claim 1 in a mold, and injects it into a material for the injection molding article. NUCLEUS MATERIAL, AND PROCESS FOR MOLDING BY INJECTION SUMMARY OF THE INVENTION A core material for injection molding, comprising a copolymer of a polyvinyl alcohol (PVA) and polyethylene oxide (PEO), as well as a core formed from the core material.