KR101924290B1 - Rubber composition with improved filling ability for mold and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a cleaning or release rubber composition for molds to produce molded articles, specifically molds for efficiently removing contaminants existing on devices such as molds during a semiconductor epoxy molding compound (EMC) molding process. To this end, rubber is used as a main component, and a cleansing agent or wax, a curing agent, and an inorganic filling agent, specifically thermally expanding microcapsules are mixed therein to effectively remove the contaminants on the mold. In addition, by reducing occurrence of unfilled state of rubber in a fine cavity part in the mold during an operation process, it is possible to improve filling properties.

Description

TECHNICAL FIELD [0001] The present invention relates to a rubber composition for a mold having improved filling properties and a method for producing the rubber composition.

The present invention relates to molds for the production of moldings, and in particular to cleaning or release molds for molds for efficiently removing contaminants present in devices such as molds during semiconductor EMC molding processes.

That is, it is possible to effectively remove the contaminants on the mold by mixing the cleaning agent or the wax, the curing agent and the inorganic filler, especially the thermally expanding microcapsule, with the rubber as the main component, and to prevent the rubber filling phenomenon occurring in the micro- Thereby improving the filling property.

Generally, when a product is molded using a thermosetting resin, in particular, an EMC molding process for semiconductor manufacturing requires high-quality product reliability. A mold used for molding a product by compressing and heating a thermosetting resin or the like as a raw material has a problem in that a part of the molded product is carbonized during the repeated working process and remains as a contaminant, But also causes the quality of the product to deteriorate during the continuous molding process.

Accordingly, studies have been made on a rubber composition for a mold for easily cleaning the inside of the mold without damaging the inner surface of the mold by removing the EMC reaction gas and the dregs of the release agent in the mold to remove contaminants remaining in the mold.

The rubber composition used in the prior art was added with a polymer component having a low melting point to increase the flowability of the rubber composition during the molding process to solve the non-filling. However, it is difficult to disperse low temperatures (60 to 80 degrees) in the mixing operation with the rubber composition because the particle size of the polymer component is larger than that of the inorganic filler and the melting point of the polymer component is high. When the mixing time is increased, A rubber scotch occurred when it climbed.

In the past, it was the only way to control the filling property in the mold cavity by controlling the filling property in the mold depending on the viscosity of the rubber composition, thereby carrying out cleaning and releasing operations. Also, when the depth of the cavity is deep, the amount of the rubber composition spreading laterally is larger than that of the rubber composition filled in the cavity, resulting in a large void phenomenon, thereby deteriorating the efficiency of cleaning and releasing operations. In order to solve this problem, productivity was deteriorated when the number of shots was increased.

Accordingly, there is a need for a cleaning composition for cleaning, which is easily cleaned without damaging the inner surface of the mold after EMC mold molding, which is a post-process of semiconductor assembly production, to remove contaminants remaining in the mold.

In order to facilitate the desorption of the thermosetting resin in accordance with the repetitive work, a release rubber which imparts releasability to the mold has been used. In the past, natural canobar wax or dimethylsilicone oil pulverized in a powder state was mixed with a solvent such as nucleic acid, , Spraying directly onto the surface of the mold, and a method of coating a large amount of wax into an epoxy resin compound and coating it by a low-pressure transfer molding method.

However, when the above methods are used, it is not uniformly applied to the inside of the mold, resulting in a decrease in releasability, environmental pollution due to the use of nucleic acid solvent, and excessive cost incurred in the low-pressure transfer molding method There is a need for a more improved release rubber.

KR 10-0454389 KR 10-2011-0009873

An object of the present invention is to increase the volume of a rubber composition in a mold during the mold working process by adding thermally expanding microcapsules, thereby improving the filling property of the microcavities in the mold.

The rubber composition for a mold having improved filling properties according to the present invention is characterized by comprising 20 to 70 parts by weight of a rubber mixture, 0.5 to 20 parts by weight of a cleaning agent or wax, 0.2 to 5 parts by weight of a curing agent, And 70 parts by weight, wherein the composition comprises microcapsules that expand by heat.

The rubber mixture may be selected from the group consisting of ethylene-propylene diene monomer rubber (EPDM), nitrile rubber (NR), styrene-butylene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), nitrile- A rubber, an acrylic rubber, a silicone rubber, and a butyl rubber.

The cleaning agent is one or a mixture of two or more selected from the group consisting of an amine cleansing compound, an amino alcohol cleansing compound and an imidazoline cleansing compound.

The curing agent is selected from the group consisting of 2,5-dimethyl-2,5-bis- (t-butylperoxy) hexane-3, dt-butylperoxide, 2,5- ) -Hexane, t-butyl cumyl peroxide, bis- (t-butylperoxy-i-propyl) -benzene, dicumyl peroxide, 4,4- butyl peroxybenzoate, 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, di-benzoyl peroxide, bis- (2,4-dichlorobenzoyl) Sulfur, and mixtures of two or more thereof.

The inorganic filler is at least one selected from the group consisting of silica, activated alumina, silica gel, amorphous aluminosilicate, and crystalline aluminosilicate.

And 0.1 to 10 parts by weight of a cleaning adjuvant based on 100 parts by weight of the composition, wherein the cleaning adjuvant is at least one selected from the group consisting of nonionic surfactants, alkaline hydroxides, and ethanol.

The microcapsule is contained in an amount of 1 to 30 parts by weight based on 100 parts by weight of the composition.

The microcapsules have a diameter before thermal expansion of 6 to 35 μm and a diameter of 30 to 200 μm after thermal expansion.

And the mold is a mold for manufacturing a semiconductor.

A rubber composition for a mold having improved filling properties according to the present invention comprises 20 to 70 parts by weight of a rubber mixture, 0.5 to 20 parts by weight of a cleaning agent or wax, 0.2 to 5 parts by weight of a curing agent, Preparing 20 to 70 parts by weight of the mixture; And 1 to 30 parts by weight of thermally expanding microcapsules are added to the mixture to prepare an uncured compound, followed by curing at 160 to 200 degrees for 1 to 15 minutes in a hot press.

The thermally expandable microcapsules contained in the rubber composition for a mold according to the present invention have a uniform particle size and are excellent in dispersibility and effective for efficient mixing.

In addition, the maximum particle size can be adjusted even at the mold working temperature, and the shape of the spherical particle cell is not collapsed, so that the shape is maintained and the tear strength is not lowered.

The thermal expansion microcapsule can control the size uniformly before and after the thermal expansion, so that it is possible to increase the volume uniformly according to the amount of the injection, and thus the degree of the rubber filling property can be controlled. In addition, expansion can be controlled more efficiently than when a chemical blowing agent is used.

In addition, since the particle size and thermal expansion starting temperature before and after the thermal expansion are varied according to the grade, it is advantageous to be applied to various products.

1 is a view showing a thermal expansion microcapsule contained in a rubber composition for a mold having improved filling properties according to the present invention.
2 is a view showing a method for producing a rubber composition for a mold having improved filling properties according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and how to accomplish them, will become apparent by reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims.

The terminology used herein is for the purpose of illustrating embodiments and is not intended to be limiting of the present invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. Like reference numerals designate the same or functionally similar elements throughout the specification. Accordingly, although the same reference numerals or similar reference numerals are not mentioned or described in the drawings, they may be described with reference to other drawings. Further, even if the reference numerals are not shown, they can be described with reference to other drawings.

In the cleaning or releasing rubber composition for a mold according to the present invention, 20 to 70 parts by weight of a rubber mixture, 0.5 to 20 parts by weight of a cleaning agent or wax, 0.2 to 5 parts by weight of a curing agent, To 70 parts by weight of the composition, wherein the composition comprises microcapsules (100) that expand by heat.

The rubber mixture may be selected from the group consisting of ethylene-propylene diene monomer rubber (EPDM), nitrile rubber (NR), styrene-butylene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), nitrile- A rubber, an acrylic rubber, a silicone rubber, and a butyl rubber. The rubber composition is a material which is cured in the mold due to heat and pressure and is removed in a state containing contaminants of the mold. The rubber composition for a mold having improved filling property according to the present invention is a mixture rubber made of EPDM and BR It is preferable to use it.

The cleaning agent is one or a mixture of two or more selected from the group consisting of an amine cleansing compound, an amino alcohol cleansing compound and an imidazoline cleansing compound.

Examples of the amine cleansing compound include 2-aminoethanol, 2- (2-aminoethoxy) ethanol, monoethanolamine, diethanolamine, Amino-2-ethyl-1,3-propanediol, 2-amino-2- (hydroxymethyl) -1,3-propanediol (2-amino-2- (hydroxymethyl) -1,3-propanediol), triethanolamine, triethanol amine hydrochloride, 3-amino- Amino-1-propanol, 1-amino-2-propanol, 3-amino-1,2-propanediol, 2-propanediol, 3-amino-1-propanol vinyl ether, 2-aminophenol, 2-aminopentylalcohol, Aminophenol, 4-aminophenol, 4-methyl-1, 5-dione, 2,4-triazoline-3,5-dion, 2- (dibutylamino) -ethanol, 2- (ethylamino) -ethanol, .

Examples of the amino alcohol cleansing compound include 2-hydroxybenzamide, 4-hydroxybenzamide, 2-hydroxybenzimidazole, 1- ( (2-hydroxyethyl) -peperazine, (2-hydroxyethyl) -piperidine, 1- (2-hydroxyethyl) (2-hydroxylmethyl) -2-pyrrolidine, 2,4-dihydroxy-6-methylpyrimidine, 2,4- (2,4-diamino-6-hydroxypyridine, 2-hydroxyethylhydrazine, 4- (hydroxymethyl) -imidazole ).

Examples of the imidazoline-based cleaning compound include 2-ethyl-4-methylimidazole, 1- (3-aminopropyl) -imidazole, imidazolidinone, imidazole, imidazole, imidazole, imidazole, imidazole, imidazole, imidazole, 4-imidazolmethanol, 2-imidazolethiol, 2-imidazolidinone, and the like.

The detergent is preferably a compound capable of effectively removing contaminants in the mold, and is suitably selected depending on its detergency and whether or not it is appropriately mixed with the rubber composition. Such a detergent is cured in a mold to be mixed with the rubber composition to remove contaminants, and by removing the cured rubber composition, the contaminants in the mold are removed, so that the operation is convenient and the efficiency is high.

When the mold after cleaning is used as it is, the mold is too dry to make detachment of the thermosetting resin difficult, and therefore, the wax is included in a releasing rubber to increase the releasability of the mold.

The detergent may be included in an amount of 0.5 to 20 parts by weight based on 100 parts by weight of the rubber composition. If it is less than 0.5, the cleaning effect is deteriorated. If it is more than 20, it may remain in the mold after curing, and hardening itself may be difficult.

The curing agent is selected from the group consisting of 2,5-dimethyl-2,5-bis- (t-butylperoxy) hexane-3, dt-butylperoxide, 2,5- ) -Hexane, t-butyl cumyl peroxide, bis- (t-butylperoxy-i-propyl) -benzene, dicumyl peroxide, 4,4- butyl peroxybenzoate, 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, di-benzoyl peroxide, bis- (2,4-dichlorobenzoyl) Sulfur, and mixtures of two or more thereof.

The curing agent is contained in the composition and acts as a catalyst for forming a rubber cured product by causing a crosslinking reaction between rubber molecule chains when heat is applied. It is preferable that the curing agent is contained in an amount of 0.2 to 5 parts by weight based on 100 parts by weight of the rubber composition. If it is less than 0.2, the effect of curing is insignificant. If it is more than 5, it may cause economic loss due to excessive content.

The inorganic filler is at least one selected from the group consisting of silica, activated alumina, silica gel, amorphous aluminosilicate, and crystalline aluminosilicate. These may be used alone or in combination of two or more.

Examples of the amorphous aluminosilicate include diatomaceous earth, kaolin, and clay. Examples of the crystalline aluminosilicate include about 34 kinds of natural zeolite and about 100 kinds of synthetic zeolite.

The inorganic filler generally acts as a builder, and a substance having a large attraction force or a large specific surface area can be used for a substance causing odor and haze. The rubber composition for a mold according to the present invention may contain silica, clay, calcium carbonate, zeolite and talc as fillers. The particle size of the filler is preferably 1 to 5 mu m or less, and if it exceeds 5 mu m, the workability may be deteriorated.

And 20 to 70 parts by weight of the inorganic filler based on 100 parts by weight of the rubber composition. If it is less than 20, the effect as a builder is deteriorated. If it is more than 70, the content thereof is too large, and the effect of other mixed substances such as a cleaning effect and a curing action may be deteriorated.

The rubber composition for a mold having improved filling properties according to the present invention may further comprise 0.1 to 10 parts by weight of a cleaning auxiliary agent per 100 parts by weight of the composition, wherein the cleaning auxiliary agent is selected from the group consisting of nonionic surfactants, alkaline water oxides and ethanol Or more.

The cleaning aid is contained in a smaller amount than the cleaning agent, and the irritating odor and smoke generated from the hardener and the like are suppressed, thereby improving the working environment and improving the cleaning power remarkably.

And 1 to 10 parts by weight of an additive depending on various other uses. Adjuvants such as melamine resin or cellulose or fibers may also be used as cleaning adjuncts. Cellulose and the like prevent the flow of the cleaning rubber and improve the efficiency of the cleaning process. In some cases, a colorant may be used to visually confirm whether or not the contaminant has been removed. Typical examples thereof include titanium oxide, anatase, and the like, and a mixture of one or more of them is used. Other compounds or mixtures may be added depending on the use within the range not detracting from the physical properties of the composition of the present invention.

The rubber composition for a mold having improved vibration resistance according to the present invention is characterized by comprising 1 to 30 parts by weight of microcapsules which are swelled by heat, relative to 100 parts by weight of the whole composition. If it is less than 1, the filling effect by the microcapsule is lowered, and if it is more than 30, the tear strength may be lowered.

The microcapsule 100 may be a thermally expanded microcapsule called Expancel manufactured by Akzonobel. The microcapsules have a diameter before thermal expansion of 6 to 35 μm and a diameter of 30 to 200 μm after thermal expansion. When the diameter is less than 30 탆 after the thermal expansion, the effect is reduced and the filling property in the mold is lowered. When the diameter is more than 200 탆, the size is too large and the tear strength may be lowered.

1 is a view showing a thermal expansion microcapsule contained in a rubber composition for a mold having improved filling properties according to the present invention. 1, the thermally expandable microcapsule 100 is formed of a hydrocarbon 120 in a spherical shape made of a thermoplastic polymer 110, and when heat is applied, the hydrocarbon is gasified and the thickness 130 of the thermoplastic polymer becomes thin, And the size is expanded. The thermal expansion starting temperature is preferably from 70 to 200 DEG C. The diameter and the thermal expansion starting temperature before and after thermal expansion vary depending on the grade.

2 is a view showing a method for producing a rubber composition for a mold having improved filling properties according to the present invention. Referring to FIG. 2, the rubber composition for a mold having improved filling properties according to the present invention comprises 20 to 70 parts by weight of a rubber mixture, 0.5 to 20 parts by weight of a cleaning agent or wax, 0.2 to 20 parts by weight of a curing agent, 5 parts by weight of an inorganic filler and 20 to 70 parts by weight of an inorganic filler (S210); Adding 1 to 30 parts by weight of thermally expanding microcapsules to the mixture to produce an uncured compound (S220); And curing the uncured compound in a hot press at 160 to 200 degrees for 1 to 15 minutes (S230).

The curing temperature is preferably from 170 to 190 ° C, and the curing time is more preferably from 3 to 8 minutes. If the curing temperature is out of the range, it is hard to cure and may cause deterioration of the properties of the mixed material.

The step S210 may further include 1 to 10 parts by weight of other additives. Other additives may be auxiliaries such as melamine resin or cellulose, or fibers, which may be used as cleaning adjuncts. Cellulose and the like prevent the flow of the cleaning rubber and improve the efficiency of the cleaning process. In some cases, a colorant may be used to visually confirm whether or not the contaminant has been removed. Typical examples thereof include titanium oxide, anatase, and the like, and a mixture of one or more of them is used. Other compounds or mixtures may be added depending on the use within the range not detracting from the physical properties of the composition of the present invention.

The step S230 may include the step of expanding the microcapsules by heat. Therefore, it is preferable that sufficient time is given to allow the thermoplastic polymer constituting the microcapsules to expand to an appropriate size.

The thermally expandable microcapsules contained in the rubber composition for a mold according to the present invention have a uniform particle size and are excellent in dispersibility and effective for efficient mixing.

In addition, the maximum particle size can be adjusted even at the mold working temperature, and the shape of the spherical particle cell is not collapsed, so that the shape is maintained and the tear strength is not lowered.

The thermal expansion microcapsule can control the size uniformly before and after the thermal expansion, so that it is possible to increase the volume uniformly according to the amount of the injection, and thus the degree of the rubber filling property can be controlled. In addition, expansion can be controlled more efficiently than when a chemical blowing agent is used.

In addition, since the particle size and thermal expansion starting temperature before and after the thermal expansion are varied according to the grade, it is advantageous to be applied to various products.

Accordingly, the rubber composition for a mold according to the present invention has the effect of efficiently removing contaminants present in a mold for molding a molded article, particularly a mold, during a semiconductor EMC molding process.

In addition, the rubber composition for a mold according to the present invention effectively removes contaminants on the mold, including thermally expanding microcapsules, and improves the filling property by improving the rubber filling phenomenon occurring in the micro-cavity portion in the mold during the working process .

Hereinafter, the present invention will be described by way of examples, but the present invention is not limited thereto.

<Examples> Thermal expansion Microcapsules  Included For mold  Preparation of rubber composition

Example 1

70 parts by weight of BR, 30 parts by weight of EPDM, 1 part by weight of stearic acid, 5 parts by weight of titanium dioxide, 30 parts by weight of silica, 7 parts by weight of a cleaning agent, 2 parts by weight of a curing agent and 5 parts by weight of thermally- To prepare an uncured mixture, followed by curing at 180 DEG C for 5 minutes in a hot press to prepare a rubber composition for mold cleaning.

Example 2

Rubber composition was prepared in the same manner as in Example 1, except that 10 parts by weight of thermally expanding microcapsule was contained.

Example 3

A rubber composition was prepared in the same manner as in Example 1, except that 15 parts by weight of thermally expanding microcapsules were contained.

Example 4

A rubber composition was prepared in the same manner as in Example 1 except that 20 parts by weight of thermally expanding microcapsules were used.

Example 5

A rubber composition was prepared in the same manner as in Example 1, except that 30 parts by weight of thermally expanding microcapsules were used.

Example 6

A rubber composition was prepared in the same manner as in Example 1 except that 40 parts by weight of thermally expanding microcapsules were used.

<Comparative Example>

Comparative Example 1

The rubber composition was prepared in the same manner as in Example 1 except that the thermally expanding microcapsules were not included.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Butadiene rubber (BR) 70 70 70 70 70 70 70 Ethylene-propylene diene monomer rubber (EPDM) 30 30 30 30 30 30 30 Stearic acid One One One One One One One Titanium dioxide 5 5 5 5 5 5 5 Silica 30 30 30 30 30 30 30 detergent 7 7 7 7 7 7 7 Hardener 2 2 2 2 2 2 2 Thermally-expanded microcapsules 5 10 15 20 30 40 -

Experimental Example

Experimental Example 1 Filling property  And Phosphorus strength  Test results

The fillability and tear strength of the rubber composition for a mold according to an embodiment of the present invention were tested. The mixture prepared in Examples 1 to 6 and Comparative Example 1 was charged into an experimental mold (MQFP 28 x 28) contaminated with an epoxy molding compound (EMC) and cured at 180 ° C and 60 kg / cm ² pressure for 5 minutes, The mold was cleaned. This operation was repeated until the contaminants on the mold were completely removed.

The results are shown in the following Table 2 by dividing the results into relatively good (G) and poor (P).

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Filling property G G G G G G P Phosphorus strength G G G G G P (rubber chipping occurs) G

(* G: Good, P: Poor)

It was confirmed that Examples 1 to 6, which are the rubber compositions for molds prepared according to the present invention, are superior in filling property as compared with Comparative Examples not containing microcapsules. However, in Example 6, which is outside the numerical range of 1 to 30 parts by weight with respect to 100 parts by weight of the total composition, which is a ratio of the thermal expansion microcapsules according to the present invention, too much microcapsules are contained, It was confirmed that the tear strength was lower.

Accordingly, it has been confirmed that the rubber composition for a mold according to the present invention contains 1 to 30 parts by weight of thermally expanding microcapsules, thereby improving fillability and excellent tear strength.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood. It is therefore to be understood that the above-described embodiments are illustrative and not restrictive in every respect.

Accordingly, the spirit of the present invention should not be construed as being limited to the above-described embodiments, and all of the equivalents or equivalents of the claims, as well as the claims set forth below, belong to the scope of the present invention will be.

100: thermally expanding microcapsules 110: thermoplastic polymer
120: hydrocarbon 130: thickness of thermoplastic polymer

Claims (11)

A cleaning or releasing rubber composition for a mold, comprising, based on 100 parts by weight of the composition,
20 to 70 parts by weight of the rubber mixture,
0.5 to 20 parts by weight of a detergent,
20 to 70 parts by weight of an inorganic filler and
0.2 to 5 parts by weight of a curing agent,
Said composition comprising heat-expandable microcapsules;
Wherein the microcapsules have a pre-thermal expansion diameter of 6 to 35 占 퐉, a diameter after thermal expansion of 30 to 200 占 퐉,
Wherein the microcapsule is in the form of a spherical particle cell and has a uniform particle size.
The method according to claim 1,
Wherein the microcapsule is contained in an amount of 1 to 30 parts by weight based on 100 parts by weight of the composition.
delete The method according to claim 1,
The rubber mixture may be selected from the group consisting of ethylene-propylene diene monomer rubber (EPDM), nitrile rubber (NR), styrene-butylene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), nitrile- Wherein the rubber composition is one or a mixture of two or more selected from the group consisting of rubber, acrylic rubber, silicone rubber and butyl rubber.
The method according to claim 1,
Wherein the detergent is one or a mixture of two or more selected from the group consisting of an amine cleansing compound, an amino alcohol cleansing compound and an imidazoline cleansing compound.
The method according to claim 1,
The curing agent is selected from the group consisting of 2,5-dimethyl-2,5-bis- (t-butylperoxy) hexane-3, dt-butylperoxide, 2,5- ) -Hexane, t-butyl cumyl peroxide, bis- (t-butylperoxy-i-propyl) -benzene, dicumyl peroxide, 4,4- butyl peroxybenzoate, 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, di-benzoyl peroxide, bis- (2,4-dichlorobenzoyl) Sulfur, and mixtures of two or more thereof.
The method according to claim 1,
Wherein the inorganic filler is at least one selected from the group consisting of silica, activated alumina, silica gel, amorphous aluminosilicate, and crystalline aluminosilicate.
The method according to claim 1,
Further comprising 0.1 to 10 parts by weight of a cleaning adjuvant based on 100 parts by weight of the composition,
Wherein the cleaning adjuvant is at least one selected from the group consisting of nonionic surfactants, alkaline water oxides and ethanol.
The method according to claim 1,
Wherein the mold is a mold for producing a semiconductor.
(a) preparing a mixture comprising 20 to 70 parts by weight of a rubber mixture, 0.5 to 20 parts by weight of a cleaning agent, 20 to 70 parts by weight of an inorganic filler, and 0.2 to 5 parts by weight of a curing agent, based on 100 parts by weight of the total composition;
(b) adding 1 to 30 parts by weight of thermal expansion microcapsules to the mixture to prepare an uncured compound; And
(c) curing the uncured compound at 160 to 200 degrees for 1 to 15 minutes in a hot press,
The microcapsules have a uniform particle size,
It is possible to control the maximum particle size even at the molding process temperature,
The shape of the spherical particle cell is not collapsed and the shape is maintained,
Wherein a uniform size control can be performed before and after thermal expansion, and a volume can be uniformly increased in accordance with the amount of injection.
11. The method of claim 10,
Wherein the step (c) comprises expanding the microcapsule by heat.

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