JPH08183055A - Injection molding method for thermoplastic resin - Google Patents

Abstract

PURPOSE: To obtain a molded product excellent in releasability of the molded product from molds and remarkably good in the surface precision and luster of the molded product by disposing the molds for injection molding, which are made of a silicone rubber, in matrices having rigidity as telescopic molds and injecting a thermoplastic resin into a cavity between the molds for injection molding. CONSTITUTION: A liquid photosetting silicone rubber composition is set on the basis of CAD data by utilizing a photoshaping system, and molds 12, 13 for injection molding, which are made of a silicone rubber whose hardness (hardness tester: A type) is 35-70 as specified in JIS K6301, are formed. These molds 12, 13 for injection molding are disposed, as telescopic molds, in matrices 14, 15 having rigidity. Then, the molds thus disposed are fixed with a bottom plate 16, a top plate 17 and a locating ring 18, and a thermoplastic resin is injected under an injection pressure of at most 300kg/cm<2> into a cavity 19 between the molds 12, 13 for injection molding through a sprue 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic resin injection molding method suitable for producing a prototype using a thermoplastic resin or for producing a small amount of a molded product.

[0002]

2. Description of the Related Art Conventionally, there has been known a method of producing an injection molding die by a so-called stereolithography system in which a photocurable resin is cured by pattern irradiation of a laser based on CAD data to produce a three-dimensional shape. (Kaihei 5-131504, etc.). Then, as the photocurable resin in this method, an epoxy acrylic photocurable resin, a urethane acrylic photocurable resin, and an acrylic photocurable resin have been used. However, molding dies produced using these resins have the drawbacks that they have poor mold releasability from the thermoplastic resin molded product, and that the surface precision of the molded product is difficult and the surface gloss is poor.

Conventionally, it has been disclosed that a silicone rubber mold is used as a nest of an injection molding mold (Japanese Patent Laid-Open No. 52-5863). However, in this injection molding method, a master model of a product to be obtained is prepared in advance, and a curable silicone composition is cast into the master model to prepare an injection mold, which is extremely disadvantageous in that it takes a lot of work time. There is. In addition, when the hardness of the silicone rubber forming the injection mold is high, the transferability of the master model is poor, and when an undercut molded product is injection molded, there are drawbacks such as defective molding. Has the drawback that the injection mold will be damaged if the injection pressure is too high.

[0004]

DISCLOSURE OF THE INVENTION An object of the present invention is to produce a silicone rubber mold which is easy to work in injection molding of a thermoplastic resin, and is excellent in mold releasability between the molded product and the molded product. An object of the present invention is to provide an injection molding method capable of producing a molded product having extremely excellent surface accuracy and surface gloss.

[0005]

According to the present invention, (a) a liquid photocurable silicone rubber is prepared by a light molding method based on CAD data of the shape and size of an injection mold designed by three-dimensional CAD. The composition is pattern-irradiated and JIS K 6
301, a step of forming the injection molding die made of silicone rubber having a hardness (testing machine: A type) of 35 to 70, and (b) a mother die having rigidity with the formed injection molding die as a nest. And the thermoplastic resin is injected into the cavity of the injection molding die at an injection pressure of 300 kg / cm ² or less.

The present invention will be described in detail below. Process for Obtaining Injection Mold Made of Silicone Rubber (Stereolithography Method and System) The injection molding die used in the present invention is a stereolithography method, and the shape and size of the injection molding die designed by three-dimensional CAD are used. The liquid photocurable silicone rubber composition is patterned and irradiated with light based on CAD data.

In the stereolithography method used in the present invention, for example, as shown in FIG. 1, a light source 1, an optical shutter 2, a mirror 3,
Optical system such as lens 4; CAD data 5, arithmetic processing unit 6
Control system for liquid photocurable resin 7, photocurable resin container 8, substrate 9, substrate support 10, three-dimensional NC table 11
A stereolithography system including a mechanism including a resin tank system such as the above can be used.

Such a stereolithography system has the following three features. (I) A three-dimensional CA relating to the shape and size of the injection molding die, mainly in the control system of the CAD data 5, arithmetic processing unit 6 and the like.
A step of converting the D data into data of a plurality of slices obtained by dividing the injection molding die by a plurality of parallel sections, (ii) based on data of one of the plurality of slices,
For example, on the liquid photocurable resin 7 layer spread on the substrate 9,
Light from the light source 1 is selectively irradiated through the optical shutter 2, the mirror 3, and the lens 4 to form a cured product layer of the composition on the substrate 9 in a shape corresponding to the shape of the slice at the one end. Step (iii), after newly developing a liquid photocurable resin 7 layer on the cured product layer, based on data of slices adjacent to the slice, on the composition layer in the same manner as described above. Selectively irradiating light, on the cured product layer, a step of forming a cured product layer of the composition in a shape corresponding to the shape of the adjacent slice, and (iv) the step of (iii), It is possible to perform the step of repeatedly stacking the cured material layers in order until the final slice and forming the injection molding die made of the cured resin on the substrate 9.

Further, in the above-mentioned stereolithography system, in order to spread the liquid photo-curable resin 7 layer on the substrate 9 or to spread the liquid photo-curable resin 7 layer on the cured material layer, for example, calculation A method of pushing up the photocurable resin container 8 with the three-dimensional NC table 11 by the signal A from the processing device 6 and moving the substrate 9 toward the bottom of the photocurable resin container 8 relatively,
Alternatively, a method of raising a liquid level of the liquid photocurable resin 7 in the photocurable resin container 8 by opening a liquid photocurable resin injection electromagnetic valve (not shown) in response to a signal B from the arithmetic processing unit 6 is adopted. can do.

Further, based on the slice data,
To selectively irradiate the liquid photo-curable resin 7 layer with light, for example, a drive device that opens and closes the optical shutter 2 by a signal C from the arithmetic processing device 6 and displaces the angle of the mirror 3 by a signal D. A method of changing the mirror angle (not shown) can be adopted.

The light may be any light in a broad sense capable of curing the liquid photocurable silicone rubber composition described later, and examples thereof include electron beams, X-rays, ultraviolet rays or light having a wavelength of 280 to 650 nm. Is mentioned. Further, as a light source for irradiating such light, for example, He-Cd
A laser, an argon ion laser, a nitrogen ion laser, a multi-frequency Nd-YAG laser, etc. are mentioned.

A specific example of such a stereolithography system is, for example, a solid creation system (DM).
EC company), SOUP (C-MET company), SLA (Japan 3D Systems company), SOLIFORM (Du P)
ont) and the like.

(Liquid Photocurable Silicone Rubber Composition) The present invention cures a liquid photocurable silicone rubber composition by using such a stereolithography system to obtain JIS K 63.
The injection molding die is made of silicone rubber having a hardness (testing machine: A type) defined by No. 01 of 35 to 70. If this hardness is too low, the resin pressure during injection molding will
The injection mold causes significant deformation, and it is not possible to obtain an accurate molded product. If the hardness is too high, the moldability of the undercut molded product deteriorates.

The liquid photocurable silicone composition used in the present invention is not particularly limited as long as it has a hardness within the above-mentioned hardness range after photocuring, and examples thereof include the following compositions. (A) 100 parts by weight of organopolysiloxane having at least two hydroxyl groups in one molecule; (B) general formula

[0015]

Embedded image

(In the formula, R is independently a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a neopentyl group, a hexyl group, a heptyl group, an octyl group. , Alkyl groups such as decyl group; alkenyl groups such as vinyl group, allyl group; aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group; cycloalkyl groups such as cyclopentyl group, cycloheptyl group, cyclohexyl group; benzyl Groups, phenylethyl groups, aralkyl groups such as methylbenzyl groups, or a part or all of the hydrogen atoms bonded to carbon atoms of these groups are substituted with halogen atoms, cyano groups, alkoxy groups, etc., for example, chloromethyl groups , Chloropropyl group, bromoethyl group, trifluoropropyl group, cyanoethyl group, A group such as a xyethyl group or an ethoxyethyl group, preferably an unsubstituted or substituted monovalent saturated hydrocarbon group having 1 to 10 carbon atoms, particularly 1 to 8 carbon atoms, which does not contain an aliphatic unsaturated group such as a vinyl group. , A is 0 or 1,
b is 2 or 3, c is 0, 1 or 2 and a + b + c = 4)

An organosilicon compound such as an organoisopropenyloxysilane having 3 or 4 hydrolyzable functional groups such as an isopropenyloxy group and an alkoxy group represented by or a partially hydrolyzed condensate thereof. 30 parts by weight, preferably 2 to 15 parts by weight;

(C) The mercapto group is 0.1 to 20, preferably 0.5 to 1 per propenyloxy group of the component B).
~ 5 mercapto group-containing organopolysiloxane having at least 2 mercapto groups in one molecule; (D) 0.01 to 10 parts by weight, preferably 0.
1 to 5 parts by weight; and (E) sensitizer 0.01 to 10 parts by weight, preferably 0.
A photocurable silicone composition comprising 1 to 5 parts by weight. The component (A) of this composition has, for example, a general formula:

[0019]

Embedded image

(In the formula, R ¹ and R ² are respectively the above R
An unsubstituted or substituted monovalent hydrocarbon group similar to those exemplified as, for example, an alkyl group such as a methyl group, an ethyl group and a propyl group; a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a butenyl group, An alkenyl group such as a henicenyl group; an aryl group such as a phenyl group or a tolyl group; a cycloalkyl group such as a cyclohexyl group; an aralkyl group such as a benzyl group, or a part or all of hydrogen atoms bonded to carbon atoms of these groups The same or different unsubstituted or substituted monovalent hydrocarbon group having 1 to 8 carbon atoms, which does not contain an aliphatic unsaturated bond, is preferably selected from groups substituted with a halogen atom, a cyano group or the like, and n Is 5
Is the integer above), the viscosity at 25 ℃,
25-500,000 cSt range, preferably 1,0
It is from 00 to 100,000 cSt. The component (A) is usually a linear diorganopolysiloxane in which both terminals of the molecular chain are blocked with diorganohydroxysilyl groups and basically the main chain is composed of repeating diorganosiloxane units. Is generally. Also, (A)
The component is a cyclic structure composed of diorganosiloxane units,
Branched structure or tri-dimensional network resin (varnish) containing trifunctional siloxane units and / or SiO ₂ units
It may be one. Specific examples of the component (A) include, for example,

[0021]

Embedded image

(However, in the above formula, g, h, i, j and k
Are positive integers that respectively satisfy the above viscosity range,
g is preferably 5 to 4000, more preferably 10
0 to 1000, h is preferably 5 to 2000, more preferably 100 to 800, and i is 3 to 50.
0 is preferable, more preferably 100 to 200, j is preferably 3 to 500, and more preferably 1
0 to 200, k is preferably 5 to 1000, and more preferably 10 to 500). Specific examples of the component (B) include, for example,

[0023]

[Chemical 4]

A hydrolyzable group-containing organosilane compound represented by, for example, and partially hydrolyzed condensates thereof (ie,
Examples thereof include organosiloxane compounds condensed by leaving three or more hydrolyzable groups in the molecule.

The above-mentioned component (C) is
(B) Crosslinks with the propenyloxy group in the component to increase the composition to a viscosity of raw rubber, and is usually bonded to a silicon atom through an alkylene group such as ethylene group or propylene group in the molecule. It is a linear, cyclic, or branched organopolysiloxane containing at least two, preferably three or more mercapto groups in the molecule. Such an organopolysiloxane may have the mercapto group bonded to a silicon atom at the terminal of the molecular chain or a silicon atom in the middle of the molecular chain via an alkylene group. Further, other substituents bonded to the silicon atom in the molecule include unsubstituted or substituted monovalent hydrocarbon groups similar to R ¹ and R ² and alkoxy groups such as methoxy group, ethoxy group and propoxy group. However, a methyl group, a methoxy group and a phenyl group are preferable. The (C) component mercapto group-containing organopolysiloxane has a viscosity at 25 ° C. of usually 0.5 to 1000 cP, preferably 1 to 1
00cP, for example, the following formula

[0026]

Embedded image

(In the formula, L is an integer of 3 or more and satisfies the above viscosity range, m, n and p are 0 or an integer of 1 or more, and q is an integer of 2 or more, each of which is in the above viscosity range. L is preferably 3 to 40, more preferably 3 to 20, and m + n + p is 0 to 300.
Is preferred, more preferably 2-100, and m +
n + q is preferably 2 to 300, and more preferably 2 to 300.
100) and the like, and these may be used alone or in combination of two or more kinds.

The curing catalyst for the component (D) is for promoting the condensation curing reaction between the component (A) and the component (B) in the presence of moisture, for example, lead-2-ethyloctane. Tetravalent tin carboxylates such as tate, dibutyltin diacetate, dibutyltin dilaurate, butyltin tri-2-ethylhexoate, iron-2-ethylhexoate, cobalt-2-ethylhexoate, Manganese-2-ethylhexoate, zinc-2-ethylhexoate, titanium naphthenate, zinc naphthenate, cobalt naphthenate, zinc stearate, lead, tin, iron, cobalt, manganese, zinc, titanium, etc. Metal organic carboxylic acid metal salt;
Organic titanate esters such as tetrabutyl titanate, tetra-2-ethylhexyl titanate, triethanolamine titanate and tetra (isopropenyloxy) titanate; organotitanium compounds such as organosiloxytitanium and -carbonyltitanium; alkoxyaluminum compounds, 3-amino Propyltriethoxysilane, N-
Aminoalkyl group-substituted alkoxysilanes such as (trimethoxysilylpropyl) ethylenediamine, hexylamine, amine compounds such as dodecylamine phosphate, and salts thereof; quaternary ammonium salts such as benzyltriethylammonium acetate, potassium acetate, sodium acetate, lithium oxalate. Lower fatty acids of alkali metal salts, such as
Dialkylhydroxyamines such as dimethylhydroxyamine and diethylhydroxyamine; tetramethylguanidine, the following formula

[0029]

[Chemical 6]

(However, Me is a methyl group, the same shall apply hereinafter) and the like, and guanidyl compound-containing silanes or siloxanes and the like. Among them, guanidine compounds, guanidyl group-containing silanes and siloxane compounds are the curing reaction. Is preferable, and it also has a function of improving adhesiveness, which is preferable. The catalysts may be used alone or in combination of two or more.

The photosensitizer of the component (E) is for promoting the reaction between the propenyloxy group in the component (B) and the mercapto group in the component (C) under ultraviolet irradiation. , Acetophenone, propiophenone, benzophenone, xanthol, fluorein, benzaldehyde, anthraquinone, triphenylamine, carbazole, 3-methylacetophenone, 4-methylacetophenone, 3-pentylacetophenone, 4-methoxyacetophenone, 3-bromoacetophenone, 4-allyl acetophenone, p-diacetylbenzene, 3-methoxybenzophenone, 4-methylbenzophenone, 4-
Chlorobenzophenone, 4,4'-dimethoxybenzophenone, 4-chloro-4'-benzylbenzophenone,
2,2-diethoxyacetophenone, 3-chloroxanthone, 3,9-dichloroxanthone, 3-chloro-
Examples thereof include 8-nonylxanthone, benzoin, benzoin methyl ether, benzoin butyl ether, bis (4-dimethylaminophenol) ketone, benzyl methoxy ketal, and 2-chlorothioxanthone. (F) 100 parts by weight of organosiloxane having at least two vinyl groups in one molecule;

(C) 0.1 to 20, preferably 0.5 to 5, mercapto groups per 1 vinyl group of the component (F).
And (E) the sensitizer in an amount of 0.01 to 10 parts by weight, preferably 0. mercapto group-containing organosiloxane having at least two mercapto groups in one molecule.
A photocurable silicone composition comprising 1 to 5 parts by weight. As the vinyl group-containing polysiloxane of the component (F),
For example, the general formula

[0033]

[Chemical 7]

(In the formula, R ¹ , R ² , R ³ and R ⁴ are each an unsubstituted or substituted monovalent hydrocarbon group similar to those exemplified as R above, for example, a methyl group, an ethyl group, Alkyl group such as propyl group; alkenyl group such as vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, hexenyl group; aryl group such as phenyl group and tolyl group; aralkyl group such as benzyl group; cyclohexyl group etc. Or a same or different unsubstituted or substituted hydrocarbon group selected from a group in which a part or all of hydrogen atoms bonded to carbon atoms of these groups are substituted with a halogen atom, a cyano group or the like. Yes, d is 1, 2 or 3, e, f is 0, 1 or 2, d + e + f = 3
And n is an integer of 5 or more and Vi is a vinyl group) is a polysiloxane containing at least 2 or more groups represented by the formula, and has a viscosity at 25 ° C. of 25 to 50.
Range of 20,000 cSt, preferably 1,000-10
It is 10,000 cSt. The component (F) is usually a linear diorganopolysiloxane in which both terminals of the molecular chain are blocked with vinyldiorganosilyl groups and the main chain is basically composed of repeating diorganosiloxane units. Is generally. Further, the component (F) may have a cyclic structure composed of a diorganoxane unit, a branched structure containing a trifunctional siloxane unit and / or a SiO ₂ unit, or a three-dimensional network resin (varnish). Said
Specific examples of the component (F) include, for example,

[0035]

Embedded image

(However, in the above formula, t, s, u, and v are positive integers which satisfy the above viscosity range.) And the like. As the component (C) and the component (E), the same components as the component (C) and the component (E) of the composition can be used. (A) 100 parts by weight of organopolysiloxane having at least two hydroxyl groups in one molecule; (G) the following general formula

[0037]

[Chemical 9]

(In the formula, R ³ is a hydrogen atom or a methyl group, R ⁴ is a methylene group, an ethylene group, a propylene group,
Alkylene groups such as tetramethylene group, hexamethylene group and methylethylene group; arylene groups such as phenylene group,
Alternatively, it may be a group formed by combining these groups, preferably having 1 to 10 carbon atoms, and more preferably 2 carbon atoms.
A divalent hydrocarbon group of 6, the same as R ⁵ and R ⁶ are exemplified as R mentioned above, respectively, 1 to carbon atoms
8 same or different unsubstituted or substituted monovalent hydrocarbon groups, preferably alkyl groups such as methyl group, ethyl group, propyl group; vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, hexenyl An alkenyl group such as a group; an aryl group such as a phenyl group and a tolyl group; a cycloalkyl group such as a cyclohexyl group; an aralkyl group such as a benzyl group; or a part or all of the hydrogen atoms bonded to the carbon atoms of these groups. An alkoxy group represented by the same or different type of unsubstituted or substituted hydrocarbon group selected from groups substituted with atoms, cyano groups, etc., and d is an integer of 0, 1 or 2) 0.1 to 30 parts by weight, preferably 0.5 to 15 parts by weight of a (meth) acrylic functional silane having a functional group;

(H) The following general formula SnX ₂

[In the formula, X is the same or different halogen atom (chlorine, bromine, iodine, etc.) and a group -OR ⁷ (provided that R ⁷ is a hydrogen atom or an unsubstituted or substituted one similar to the above R). A valent hydrocarbon group, preferably an alkyl group such as a methyl group, an ethyl group and a propyl group; an alkenyl group such as a vinyl group and an allyl group; an aryl group such as a phenyl group and a tolyl group; a cycloalkyl group such as a cyclohexyl group; or These are the same or different unsubstituted or substituted hydrocarbon groups selected from groups in which some or all of the hydrogen atoms bonded to the carbon atoms of these groups are substituted with halogen atoms, cyano groups, etc.), or a group- OCOR ⁷ (provided that R ⁷ has the same meaning as above)] and a divalent tin compound 0.01 to 10
Parts by weight, preferably 0.1 to 5 parts by weight; (I) the following general formula (4)

[0041]

[Chemical 10]

(In the formula, R ⁹ and R ¹⁰ are each a methyl group or an ethyl group, and R ¹¹ , R ¹² , and R ¹³ are each a hydrogen atom or the same as those exemplified above for R;
Usually, same or different, unsubstituted or substituted monovalent hydrocarbon groups having 1 to 10 carbon atoms, preferably alkyl groups such as methyl group, ethyl group, propyl group; alkenyl groups such as vinyl group, allyl group; phenyl group , An aryl group such as a tolyl group; a cycloalkyl group such as a cyclohexyl group; or the same kind or a group selected by substituting a part or all of hydrogen atoms bonded to carbon atoms of these groups with a halogen atom, a cyano group or the like, or Alkoxy-α-silyl ester represented by different kinds of unsubstituted or substituted hydrocarbon groups, and e is an integer of 0, 1 or 2. 0.1 to 30 parts by weight, preferably 0.5 to 15 parts by weight Parts; (D) curing catalyst 0.01 to 10 parts by weight, preferably 0.
1 to 5 parts by weight; and (E) sensitizer 0.01 to 10 parts by weight, preferably 0.
A photocurable silicone composition comprising 1 to 10 parts by weight.

The component (A) of this composition may be the same as the component (A) of the above composition.

Specific examples of the component (G) include, for example:

[0045]

[Chemical 11] Etc.

Specific examples of the divalent tin compound as the component (H) include, for example, SnCl ₂ , SnBr ₂ , Sn.
I ₂ , Sn (OCOCH ₃ ) ₂ , Sn (CO ₂ ) ₂ , S
n (OCOC ₇ H ₁₅ ) ₂ , Sn (OMe) ₂ , Sn (O
COC ₁₅ H ₃₁ ) _{2 and the} like. Specific examples of the alkoxy-α-silyl ester of the component (I) include, for example,

[0047]

[Chemical 12] (However, the Me is methyl, Et is ethyl group, ⁿ Bu is a is n- butyl group).

As the component (D) and the component (E), the same components as the component (D) and the component (E) of the composition can be used.

A filler may be added to the liquid photocurable silicone rubber composition used in the present invention for the purpose of imparting appropriate mechanical properties to the silicone rubber obtained by curing the composition. Examples of the filler include fumed silica, pyrogenic silica, precipitated silica, fumed titanium oxide, carbon black, calcium carbonate, diatomaceous earth, calcium silicate, and organochlorosilanes thereof, polyorganosiloxane, hexamethyldisilazane. And the like, which have been subjected to a hydrophobic treatment with, for example. The blending amount of the filler is such that the base polymer of the composition, for example, the component (A) or the component (F) 10
300 parts by weight or less, for example, 10 to 20 parts by weight, relative to 0 parts by weight
About 0 parts by weight is preferable. In addition, the liquid photocurable silicone rubber composition used in the present invention, for the purpose of imparting thermal conductivity to the silicone rubber obtained by curing the composition,
For example, a thermal conductivity improving material such as quartz powder, alumina, magnesia, carbon black, graphite, metal powder may be added. As the metal powder, for example, iron, copper,
Examples thereof include fibrous substances such as aluminum, silver, gold, and nickel, flaky substances, and powdered substances, among which aluminum powder is preferable. The particle size of the aluminum powder is preferably 200 μm or less. If this particle size is too large, the surface accuracy of the mold may deteriorate.

Since the strength and the thermal conductivity of the silicone rubber are improved by adding the thermal conductivity improving material, when the injection molding mold obtained from this is used as a nest, the thickness of the mother mold is reduced. It is possible to improve the gradual cooling effect of the molten thermoplastic resin and improve the durability of the injection molding die itself.

The amount of the thermal conductivity improver compounded is 25 with respect to 100 parts by weight of the liquid photocurable silicone rubber composition.
~ 1000 parts by weight is preferable, and if the blending amount is too small,
When the strength and the thermal conductivity are insufficiently improved, and when the amount is too large, the viscosity of the composition rises, so that the molding die may not be easily manufactured.

The injection molding die used in the molding method of the present invention is produced by the above-mentioned stereolithography system using such a liquid photocurable silicone rubber composition. The injection molding die is designed by three-dimensional CAD. In this case, the minimum distance between the cavity surface of the injection molding die and the surface contacting the mother die is 30
An injection mold of about mm or less is preferable. Such 3
By injection-molding a thermoplastic resin using an injection-molding die of about 0 mm or less, the heat dissipation of the injection-molding die is improved, and there is no deformation of the die due to molding pressure.
It is possible to obtain a highly accurate molded product.

Injection Molding of Thermoplastic Resin In the molding method of the present invention, as shown in FIG. 2, for example, as shown in FIG. After arranging in the mold (14, 15), the molding mold arranged in this way is attached to the movable side mounting plate 1
6, the fixed side mounting plate 17, and the locate ring 18, and the injection molding die (12, 1,
The thermoplastic resin is injected into the cavity 19 of 3) with an injection pressure of 3
Injection is performed at 00 Kg / cm ² or less.

The rigid master mold (14, 15) may be made of metal or resin, but is preferably
A mother mold made of a metal, a thermosetting resin, or a photocurable resin having a thermal conductivity of 3 × 10 ⁻³ cal / cm · sec · ° C. or more. If this thermal conductivity is too low, the cooling time of the resin becomes long, which requires a long molding cycle, which may be economically disadvantageous.

Examples of the metallic mother die include a mother die made of carbon steel for machine structure, alloy steel for machine structure, alloy tool steel, stainless steel, aluminum alloy and the like. As the matrix of the thermosetting resin, for example, a thermosetting resin such as an epoxy resin mixed with a metal powder such as aluminum is preferable.

The master mold made of photocurable resin can be easily manufactured by the above-mentioned stereolithography system. When the matrix is made of a thermosetting resin, it is preferable to mix a thermosetting resin such as an epoxy resin with a metal powder such as aluminum.

Examples of the photocurable resin composition used for the master mold include photopolymerizable oligomers such as epoxy acrylate, urethane acrylate, polyester acrylate, and polyether acrylate; photopolymerizable oligomers such as monofunctional acrylate and polyfunctional acrylate. Examples include monomers; benzophenone-based, acetophenone-based, thioxanthone-based, perokinde-based photopolymerization initiators; amine-based and quinone-based photopolymerization initiation assistants, and the like.
Further, these photocurable resin compositions may contain a thermal polymerization inhibitor, a plasticizer, and a non-reactive polymer as other additives. Also, for the purpose of imparting thermal conductivity to the matrix,
To this photocurable resin composition, the same material as the above thermal conductivity improving material can be added.

In the molding method of the present invention, if the injection pressure is too high, the injection mold may be damaged. The resin injection rate is preferably 100 cm ³ / sec or less. If the resin injection rate is too large, the resistance of the molten resin to the injection molding die increases, and it may be difficult to inject the resin. Further, when the molding method of the present invention is applied to the production of a complicated resin molded product, the cavity 1
It is preferable to inject the molten resin into the cavity 19 after decompressing the inside 9 using a general-purpose vacuum pump. In this case, the degree of vacuum in the mold (the degree of pressure reduction from atmospheric pressure) is 300 mm.
It is preferably Hg or more. If the degree of pressure reduction is less than 300 mmHg, it may take time to control the temperature in the mold and work efficiency may deteriorate.

The thermoplastic resin injection molding machine used in the molding method of the present invention may be of a known type, and examples thereof include a hydraulic drive type and an electric type. Further, an injection molding machine capable of switching the injection pressure from low pressure to high pressure is particularly preferable.

The thermoplastic resin applicable to the present invention is not particularly limited as long as it can be injection-molded, and examples thereof include polyethylene resin, polypropylene resin, ABS (acrylonitrile-butadiene-styrene copolymer) resin, polychlorinated resin. General-purpose resin such as vinyl resin; polycarbonate resin,
Polyamide resin, polyester resin, polyacetal resin, polyphenylene sulfide resin, polyimide resin,
Super engineering plastics such as polyarylate resin; liquid crystal resin; thermoplastic elastomer and the like. Among them, polyethylene resin, polypropylene resin, and ABS resin are preferable in view of the expansion coefficient of the injection molding die, the strength when heated, and the chemical influence on the silicone rubber.

[0061]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. The viscosity is a value measured at 25 ° C.

Example 1 100 parts by weight of dimethylpolysiloxane (viscosity: 5000 cP) whose both ends were blocked with hydroxy groups, 10 parts by weight of fumed silica, 1.7 parts by weight of methacryloxypropyltrimethoxysilane, and tin dioctoate. 1 part by weight,
A liquid photocurable silicone composition containing 3 parts by weight of 2-ethylhexyl 2-trimethoxysilylpropionate, 2 parts by weight of diethoxyacetophenone, and 0.5 parts by weight of dibutyltin dilaurate was prepared.

Using this composition, injection molding molds (12, 13) made of silicone rubber as shown in FIG. 3 were produced by the stereolithography system shown in FIG. The light of the stereolithography system was laser light (ultraviolet light), and the slice layers were set to a thickness of 50 μm and laminated to produce injection molding dies (12, 13).

The hardness of the silicone rubber constituting the obtained injection molding molds (12, 13) was measured according to JIS K 6301.
It was 40 when measured in accordance with (Testing machine: A type). In addition, a cavity (14, 15) having rigidity to support the cavity portion of the injection molding die (12, 13) and the rubber die.
Was 30 mm (shown by T and T ′ in FIG. 2). As shown in FIG. 2, an injection molding die (12,
The mother die (14, 15) on which 13) is arranged is made of carbon steel S45C for machine structure and has a thermal conductivity of 0.5 cal / c.
It was m · sec · ° C.

Next, in an injection molding machine for thermoplastic resin, AB
After the S resin was charged and plasticized at 240 ° C., it was injected into the cavity 19 of the injection molding die (12, 13). The injection conditions were an injection time of 10 seconds, a cooling time of 40 seconds, an injection pressure of 300 kg / cm ² , a mold clamping pressure of 35 t, and a molding mold temperature of 60 ° C. The obtained molded product was easily peeled from the mold and had gloss and high dimensional accuracy.
Further, similarly, continuous molding was carried out to manufacture molded products, but all the molded products were glossy and had high dimensional accuracy.

[0066] In Comparative Example 1 Example 1, the injection pressure from 300 Kg / cm ^2, except that raised the 500 Kg / cm ^2, but the molten resin in the same manner as in Example 1 was injected into the cavity 19,
The injection mold (12, 13) was broken.

Comparative Example 2 100 parts by weight of dimethylpolysiloxane (viscosity: 5000 cP) blocked at both ends with hydroxy groups, 40 parts of fumed silica, 1.7 parts by weight of methacryloxypropyltrimethoxysilane, 0.1 parts of tin dioctoate. Parts by weight, 2-
2-Ethylhexyl trimethoxysilylpropionate 3
A liquid photocurable silicone composition containing 1 part by weight, 2 parts by weight of diethoxyacetophenone, and 0.5 part by weight of dibutyltin dilaurate was prepared.

Next, injection molding molds (12, 13) were produced in the same manner as in Example 1 except that this composition was used. The hardness of the silicone rubber constituting the obtained injection molding dies (12, 13) was measured in the same manner as in Example 1 and the result was 75. An ABS resin molded product was obtained in the same manner as in Example 1 except that the injection molding molds (12, 13) were used. However, since the transferability of the master model was not good, the molded product was dimensionally accurate. The quality was inferior and we could not obtain a good product.

Example 2 100 parts by weight of polydimethylsiloxane (viscosity: 1500 cP) having both ends blocked with trivinylsilyl groups, 20 parts by weight of fumed silica, the following formula

[0070]

[Chemical 13] (In the formula, n is the viscosity of this compound at 25 ° C. is 35
A liquid photocurable silicone composition was prepared by blending 5 parts by weight of a mercapto group-containing organopolysiloxane represented by the formula (1) and 1 part by weight of 2,2-diethoxyacetophenone. Next, an injection molding die (12, 1) was prepared in the same manner as in Example 1 except that this composition was used.
3) was produced. Obtained injection mold (12, 13)
As a result of measuring the hardness of the silicone rubber constituting the above in the same manner as in Example 1, it was 60.

Then, using the photo-curable resin described below, a master mold (14, 15) made of silicone rubber as shown in FIG. 2 was produced by the stereolithography system shown in FIG.

Photocurable resin for master mold bisphenol A bis (2-hydroxypropyl) diacrylate 30 parts by weight trimethylolpropane triacrylate 20 parts by weight Octylphenol polyether alcohol 1 part by weight PMMA polymer particles (manufactured by Du Pont, RCP 1674) ) 10 parts by weight Boron nitride powder 30 parts by weight 2,2-dimethoxy-2-phenylacetophenone 2 parts by weight The light of the stereolithography system is laser light (ultraviolet light), and the thickness of the slice layer is set to 50 μm. And stack
A matrix (14, 15) was prepared. The thermal conductivity of this matrix was 1 × 10 ⁻³ cal / cm · sec · ° C. Next, PP (polypropylene) resin was put into an injection molding machine for thermoplastic resin, plasticized at 240 ° C., and then injected into the molding die. Injection conditions are: injection time 10 seconds, cooling time 4
0 seconds, resin melting pressure 250 Kg / cm ² , mold clamping pressure 10
The temperature was ton and the mold temperature was 50 ° C. The obtained molded product was easily peeled from the mold and had gloss and high dimensional accuracy. Further, similarly, continuous molding was carried out to manufacture molded products, but all the molded products were glossy and had high dimensional accuracy.

[0073]

According to the present invention, in injection molding of a thermoplastic resin, it is possible to prepare a molded product which is excellent in mold releasability between a molded product and a molding die, and has a remarkably excellent surface accuracy and surface gloss.

[Brief description of drawings]

FIG. 1 is a conceptual diagram illustrating a stereolithography system used in the present invention.

FIG. 2 is a cross-sectional view illustrating the arrangement of an injection molding die and a mother die used in the present invention.

FIG. 3 is a conceptual diagram showing an injection molding die used in Examples.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location B29K 101: 12 105: 24 B29L 31:28 (72) Inventor Takafumi Sakamoto Gunma Prefecture Usui-gun Matsuida-cho Hitomi No. 1 10 Shin-Etsu Chemical Co., Ltd. Silicone Electronic Materials Research Laboratory

Claims (3)

[Claims] 1. (a) A liquid photocurable silicone rubber composition is pattern-irradiated with light based on CAD data of the shape and size of an injection molding die designed by three-dimensional CAD by a stereolithography method, and JIS A step of forming the injection molding die made of a silicone rubber having a hardness (testing machine: A type) specified in K 6301 of 35 to 70, and (b) a mother having rigidity with the formed injection molding die as a nest. Place it in a mold,
An injection molding method for a thermoplastic resin, comprising the step of injecting a thermoplastic resin into the cavity of the injection mold at an injection pressure of 300 kg / cm ² or less. 2. The minimum distance between the cavity surface of the injection molding die used in the step (b) and the surface in contact with the mother die is 30 m.
The injection molding method according to claim 1, which is less than or equal to m. 3. The mother die is made of metal, thermosetting resin, or photocurable resin, and has a thermal conductivity of 3 × 1.
The injection molding method according to claim 1 or 2, wherein the temperature is 0 ^-3 cal / cm · sec · ° C or higher.