KR920004213B1 - Thermosetting resin composition for injection molding - Google Patents

Abstract

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Description

Thermosetting resin composition for injection molding and its manufacturing method

1 is a schematic diagram of a measurement process by a disc hardening test apparatus.

사이의 관계도.2 is the first retention time and flow index in Example 1

Relationship between.

3 is the Arrhenius table of Example 1. FIG.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosetting resin composition for injection molding having a good moldability under low injection pressure due to good fluidity and thermal stability in cylinders and reactivity in a mold, and a manufacturing method thereof.

In injection molding of thermosetting resins, there is a need for materials to provide the opposite properties of lowering in-cylinder reactivity, good in-mold fluidity and rapid curing, and many methods have been proposed to improve these properties today.

As for the phenolic resin composition, additives such as furfural and styrene have been combined to improve the fluidity and thermal stability in the cylinder, but their effects are insufficient to improve the fluidity. On the other hand, when the amount of addition is increased, these additives have a disadvantage in that the curing in the mold does not proceed completely and causes defects in the properties and appearance of the molded product.

Also, when the curing agent is added to the above-mentioned system, the curing rate obtained in the mold is only slightly increased and the thermal stability of the in-cylinder system is impaired, which is undesirable.

In addition, Japanese Patent Application Laid-Open No. 18861/1979 discloses a method of combining an inorganic hydrate salt to accelerate the curing using water generated by decomposition of these hydrates in a mold, and Japanese Patent Application Laid-Open No. 137294/1978 discloses a phenolic resin. However, a method of using a conventional precured phenol resin composition mixed with at least two components selected from a curing agent and a rheology control agent is disclosed, but these methods do not provide satisfactory effects and are not actually used. Preferred properties for these materials are that fluidity is maintained, for example, by inhibiting the curing reaction at a material temperature of approximately 110 ° C. in the cylinder while the curing reaction should not be lowered at a material temperature of approximately 170 ° C. in the mold. The proposal is therefore unsatisfactory in this respect.

A first object of the present invention is to provide a resin composition suitable for injection molding of a thermosetting resin. The resin composition, for example, inhibits the curing reaction in the temperature range of approximately 110 ° C. to maintain fluidity while the curing reaction does not weaken in the temperature range of approximately 170 ° C.

It is a second object of the present invention to provide a fluidity control agent suitable for producing the resin composition described above.

It is a third object of the present invention to provide a suitable evaluation method for achieving the above object.

의 변동을 도시하는 디스크경하도표상의 유도기간후에 경화율의 현저한 변화를 지시하는 직선부경사에 의해 결정된다)이며, 적어도 26Kcal/mol의 겉보기활성에너지(여기서, 겉보기 활성에너지는 겉보기경화율의 아레니우스표에서 계산된다)를 지니는 사출성형용 열경화성수지조성물을 제공함으로써 달성된다.The above-mentioned object of the present invention consists of a phenol resin, hexamethylenetetramine, a filler, an additive and α, α'-dimethoxy-p-xylene, and has an apparent curing rate of at least 0.7 cm / sec at 170 ° C. and 110 ° C. At 0.008 cm / sec or less (where the apparent cure rate is the flow index from the change in primary retention time measured by the disc cure test device at the specified temperature.

It is determined by the linear inclination indicating a significant change in the curing rate after the induction period on the disk gradient plot showing the variation of, and the apparent active energy of at least 26 Kcal / mol (where the apparent active energy is the By molding a thermosetting resin composition for injection molding.

That is, the usual molding composition materials containing phenolic resin, nucleated methylenetetramine, filler door and additives are used in combination with α, α'-dimethoxy-p-xylene. Therefore, it is possible to obtain a phenolic resin composition for injection molding having improved flowability and thermal stability in the cylinder and excellent curability in the mold.

Phenolic resins that can be cured with hexamethylenetetramine can be used in the present invention, and representative phenolic resins are, for example, phenol, cresol, xylenol, resorcinol, bisphenol-A, p-butylphenol, p- Obtained by reacting phenols such as octylphenol and styrenated phenol with aldehydes such as formaldehyde, paraformaldehyde, trioxane and furfural; Phenolaralkyl resins derived from phenols and di-halogenated p-xylylenes such as α, α'-dichloro-p-xylene or p-xylylene dialkyl ethers such as α, α'-dimethoxy-p-xylene These phenol resins are used in a single or a mixture of two or more.

Fillers used for conventional phenolic resin compositions can also be used in the present invention. Examples of fillers include wood powder, talc, silica, clays, wollastonite, sepolite, calcium carbonate, magnesium oxide, potassium titanate, glass fibers, vinylon TM fibers, aramid TM fibers, carbon fibers, graphite and carbon black.

Additives that can be used for conventional phenolic resin compositions can also be used in the present invention. Examples of the additives include synthetic resins such as pigments, lubricants, antioxidants, curing accelerators, epoxy resins and silane binders.

In the present invention, α, α'-dimethoxy-p-xylene is used as the rheology control agent.

The amount of hexamethylenetetramine used in the present invention is usually 8 to 25 parts by weight and preferably 8 to 15 parts by weight per 100 parts by weight of the phenol resin. The aforementioned fillers are usually used in an amount of 60 to 240 parts by weight per 100 parts by weight of the phenol resin, and additives are likewise used in the range of 3 to 15 parts by weight. If the amount of the filler is 60 parts by weight or less, there is a tendency that blistering of the molded article occurs in the molding process, which is not suitable. On the other hand, if the amount of filling exceeds 240 parts by weight, it is also disadvantageous because the viscosity of the plasticized composition in the cylinder is too high to make injection difficult.

As the rheology control agent used in the present invention, the amount of α, α'-dimethoxy-p-xylene is 2 to 20 parts by weight and 3 to 15 parts by weight per 100 parts by weight of the phenol resin. If the amount is 2 parts by weight or less, the fluidity and thermal stability of the plasticized compound in the cylinder is hardly improved, and the apparent curing rate at 110 ° C exceeds 0.008 cm / sec. If the amount exceeds 20 parts by weight, the apparent curing rate at 170 ° C. decreases to 0.7 cm / sec or less, adversely affecting the appearance and quality of the molded article.

In the preparation of the resin composition of the present invention, the mixture of the phenolic resin, nucleosamethylenetetramine, filler and additives is not converted to B-stage by hot kneading before addition of the rheology control agent.

In preparing the resin composition of the present invention, the mixture is prepared from the above phenol resin, hexamethylenetetramine, fillers, additives and α, α'-dimethoxy-p-xylene, and the mixture is continuously wetted or dried by a roll, a kneader, or the like. Knead and precure.

의 12∼13cm의 범위가 되도록 선택한다.The following conditions are used for precure by the roll method, which is often carried out on dry dough. The front roll temperature is 90 ~ 100 ℃, the back roll temperature is about 50 ~ 70 ℃ when the filler is mainly composed of inorganic material, and about 120 ~ 140 ℃ when wood powder is the main component of the filler. It is -4 minutes. Molding materials can be prepared in precured sheets by conventional methods such as power mills. In a wet kneading method using a kneader or the like, wetting agents such as acetone and methanol are used in amounts of 10 to 100 parts by weight per 100 parts by weight of the phenol resin. The mixture is hot kneaded at 50-70 ° C. for 10-20 minutes and then dried at 70-90 ° C. until the wetting agent is removed to obtain a molding material. In the above-mentioned method, the thermal kneading condition is that the B-stage of the precured material is initially flowable when the first retention time is 0 at 170 ° C in the disc hardening test apparatus described later.

To be in the range of 12 to 13 cm.

The resin composition of the present invention can be converted into a thermosetting resin composition suitable for injection molding by the above-mentioned method.

The resin composition of the present invention has an apparent hardening rate of 0.7 cm / sec or higher at 170 ° C., 0.008 cm / sec or lower at 110 ° C., and is calculated from the Arenius table of the apparent hardening rate. It has an apparent active energy of at least 26 Kcal / mol.

)이 결정된다. 그러므로 예를들면, 170℃의 규정온도에서 1차보유시간의 변화로 발생된 유동지수

의 변동을 표 2의 디스크경화도표에 설명한다. 제 2 도에 도시한 바와같이, 경화율은 도표의 유도기간(도표에서 점 a-점 b)후에 현저하게 변화된다. 겉보기경화율(cm/sec)을 직선부의 경사(도포에서 점 b-점 c)에서 구할 수 있다.The disc hardening test apparatus will be described below. The test apparatus is a trade name WFA-15 manufactured by Shinto Metal Industries Ltd. As illustrated in FIG. 1, 3 g of the compound is placed on the heating plate B at which the specified temperature is maintained. The heating plate B is quickly raised to a position having a space of 1 mm with respect to the heating plate A. Both heating plates are held in position for a predetermined time (called primary holding time). Heat plate B is further raised after the first holding time. The compound is pressed to a pressure of 83 kg / cm 2 generated between both heating plates and cured for a specified time. The square of the area (s) of the cured material thus obtained is (flow index

) Is determined. Therefore, for example, the flow index generated by the change of the primary holding time at the specified temperature of 170 ° C

Variation in the following is described in the disc hardening table in Table 2. As shown in Figure 2, the cure rate changes significantly after the induction period of the plot (point a-point b in the diagram). The apparent cure rate (cm / sec) can be obtained from the slope of the straight portion (point b-point c in the application).

The apparent active energy can be calculated from the Arrhenius table (Fig. 3) of the apparent cure rate obtained at any temperature of 110 ° C to 170 ° C. The following publication can be used in connection with the calculation method of the active energy.

S. Tonogaya, "New Methods for Evaluating the Curing Properties and Flow of Thermosetting Resin and Their Application to Molding Practice" (Technical Report of Osaka City Industrial Research Institute (1983)).

As mentioned above, the resin composition of the present invention having a specific apparent curing rate and a specific apparent active energy at 170 ° C. and 110 ° C. solves the temperature dependence problem of the curing rate, which cannot be solved in the conventional proposal, and this problem has been solved. It is solved by simultaneous use.

For example, an injection molding machine for thermosetting resin is set at a cylinder front and rear surface temperature of 95 ° C., an injection pressure of 4 to 10 kg / cm 2, and a mold temperature of 170 ° C., and under such conditions, the resin composition of the present invention is a resin composition of a cylinder. Even if the residence time exceeds 4 minutes, injection molding can be performed within an injection time (mold filling time) set to 15 seconds or less.

This evaluation method using an injection molding machine for thermosetting resin in which the cylinder front and rear surface temperature is set at 95 ° C. and injection pressure of 410 kg / cm 2 can not be applied to conventionally known phenolic compounds. In addition, the resin composition does not cause a problem in the mold curing time because it has excellent curing properties than conventional compounds in the high temperature region of approximately 170 ℃.

Another characteristic of the resin composition of the present invention is that it has a high flow length of 20 cm or more in the transfer molding method at 170 ° C. and shows excellent flowability of the resin composition at high temperature. Swirl flow lengths of 20 cm or more are also achieved in the prior art, for example by adding furfural as the rheology control agent. However, since furfural must be added in large amounts to provide similar fluidity as compared to the rheology control agent of the present invention, as a result, furfural weakens the operability during the formation of the composition, in particular during the precuring step and also during the molding step. Low curability results in a disadvantage that adversely affects the quality of the molded article. Since these problems are caused by insufficient temperature dependence of the curing rate in the low temperature and high temperature range, it can be seen that the present invention requires at least 26 kcal / mol of apparent active energy based on the measurement results of the disc hardening test apparatus.

The injection molding compound obtained by using the resin composition of the present invention is excellent in fluidity and moldability under low pressure, for example, expansion of injection area in mold, increase of injection quantity, reduction of injection energy, reduction of residual stress in molded product. It is possible to reduce the gate cutting area in the mold and to reduce the size of the ball and the ball.

The excellent thermal stability of the in-cylinder molding compounds enables the improvement of molding methods such as the application of molding machines and molding processes used for injection molding of thermosetting resins, the use of so-called buffer molding and application to flashless molding. Furthermore, the use of screws with high kneading efficiency can increase the material temperature in the cylinder, reduce the molding cycle time, and many other effects are also expected.

The injection molding compound prepared in the resin composition of the present invention can naturally be used in a conventional high pressure injection molding machine. In high pressure molding, the high fluidity of the compound reduces mold filling time in precision molding and the molding cycle time can also be reduced by utilizing the exothermic phenomenon of the compound at the gate. In addition, the thermal stability of the compound can improve its operability even after long stay in the cylinder.

Therefore, various industrially valuable effects can be obtained by using the injection molding compound of the present invention.

Hereinafter, the present invention will be described in detail through Examples and Comparative Examples.

[Examples 1-3]

Novolac resin (trade names, NOVOLAC # 100HS and # 200: manufactured by Mitsui Toatsu Chemicale Inc.) and phenolaralkyl resins (trade name, MILEX XL-225; manufactured by Mitsui Totsu Chemicale Inc.) are used as phenolic resins.

The resin composition consisting of the components described in Table 1 is kneaded with 14 rows for 2 to 4 minutes. The temperature of the front roll is maintained at 90 to 100 ° C. The temperature of the rear roll is maintained at about 60 ℃ if the filler is mainly composed of inorganic materials, and approximately 140 ℃ if the filler is mainly composed of wood powder. The dough sheet thus obtained is cooled and ground in a power mill with a 6 mm screen.

The properties of the thermoset resin for injection molding thus obtained are tested. A 50 ton transfer molding machine (trade name HDF-50, manufactured by Hoshino Tokushc Inc. (1982)) is used at a mold temperature of 170 ° C., a filling pressure of 460 kg / cm 2 and a plunger speed of 40 mm / sec. The thread is molded. The swirl flow length is determined by measuring the gloss length of the thread. The sample volume of 25 g is adjusted to obtain a collection thickness of 20 mm. Use the mold designated EMIL1-66 and the curing time is 2 minutes.

의 변동을 설명하는 디스크경화도표를 얻는다.Flow index generated by changing the primary holding time by operating a disc hardening tester (trade name WFA-15 Shinto Metal Industries Ltd. (1979)) as described above.

Obtain a disc hardening diagram that explains the variation of.

The apparent cure rate is determined by measuring the slope of the straight line indicating a significant change in cure rate after the induction period of the curve, and the apparent active energy is calculated from the Areneus table of the apparent cure rate.

An injection molding machine (trade name IR 45P, manufactured by Toshiba Machine Inc. (1981)) having a fixing force of 45 tons is used with a mold temperature of 170 ° C, a front and rear cylinder temperature of 95 ° C, and an injection pressure of 410kg / cm 2. In-cylinder thermal stability is indicated by the maximum residence time of the compound in the cylinder that can fill the mold within 15 seconds. The mold used is a JIS model mold having a co-volume of 42 cm 3 to produce specimens with flexural strength, Charpy impact strength and water absorption. The minimum curing time without blistering on the specimen for Charpy impact strength is measured every 5 minutes. The results obtained are summarized in Table 1.

Comparative Examples 1 to 13

1-7 are performed for comparison according to the process of Examples 1-3 using various fluidity regulators.

Comparative Examples 8 to 10 are run in the same procedure as described in Examples 1 to 3, respectively, without using a rheology modifier.

Comparative Examples 11 and 12 are carried out in the same manner as in Example 1 described above, except for using the previously used additives such as propral and styrene instead of α, α'-dimethoxy-p-xylene. .

Comparative Example 13 is the above-described Example 1 in addition to the addition of α, α'-dimethoxy-p-xylene and novolak resin to the phenol compound precured according to the procedure disclosed in Japanese Patent Application Laid-Open No. 137294/1978. Run the same process as

The properties of these thermosetting resin compositions for injection molding are measured. The results of the swirl flow length, apparent cure rate and apparent active energy at 110 ° C. and 170 ° C., in-cylinder thermal stability and cure time are summarized in Table 1.

TABLE 1

Claims (2)

It consists of 8-25 weight part of hexamethylenetetramine, 60-240 weight part of fillers, 3-15 weight part of additives, and 2-20 weight part of (alpha), (alpha) 'dimethoxy- p-xylenes with respect to 100 weight part of phenol resins, ; Flow index from apparent change in primary retention time measured with disc hardening tester at specified temperature

When determined by the inclination of the straight portion indicating a significant change in the curing rate after the induction period on the disc hardening diagram showing the variation of?, It is 0.7 cm / sec or more at 170 ° C. and 0.008 cm / sec or less at 110 ° C .; A thermosetting resin composition for injection molding, wherein the apparent active energy is at least 26 kcal / mol when calculated from the Arenius Table of the apparent cure rate. Flow index from apparent change in primary retention time measured with disc hardening tester at specified temperature

When determined by the inclination of the linear portion indicating a significant change in the cure ratio after the induction period on the disc hardening diagram showing the variation of, the apparent active energy is not less than 0.7 cm / sec at 170 ° C and less than 0.008 cm / sec at 110 ° C. In order to obtain a thermosetting resin composition of at least 26 kcal / mol as calculated from the Areneus table of apparent curing rate, 2 to 20 parts by weight of α, α'-dimethoxy-p-xylene are used in 100 parts by weight of phenol resin and 8 to hexamethylenetetramine. A method for producing an injection molding thermosetting resin composition comprising 25 parts by weight, 60 to 240 parts by weight of a filler and 3 to 15 parts by weight of an additive, and preliminarily curing the obtained mixture by dry or wet dough.

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