JPH09176259A - Phenolic resin molding material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the flowability and the thermal stability in a cylinder without impairing the curability by using as the constituent a phenolic resin having the phenolic hydroxyl groups allowed to cause urethane formation with an isocyanate compound. SOLUTION: This phenolic resin molding material having an equivalent ratio of urethane groups to phenolic hydroxyl groups of (5:95) to (40:60) is obtained by reacting 5-50% of the phenolic hydroxyl groups of a phenolic resin comprising a novolak or resol phenolic resin or a mixture thereof with an isocyanate compound, such as ethyl, propyl or butyl isocyanate, in an organic solvent at ordinary temperature in the presence of a reaction catalyst. This molding material in an amount of 100 pts.wt. in terms of resin component is mixed with 30-250 pts.wt. organic filler comprising, e.g. wood flour, pulp, fabric chips or polyvinyl alcohol fibers, or an inorganic filler comprising, e.g. calcium carbonate, aluminum hydroxide or silica, and a curing agent, a curing aid, a release agent, etc., the mixture is heated and kneaded, and the kneaded material is granulated if necessary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phenol resin molding material which is excellent in molding processing, and particularly to a phenol resin molding material which is excellent in thermal stability in a cylinder.

[0002]

2. Description of the Related Art Generally, a phenol resin molding material for injection molding must have sufficient fluidity and thermal stability in a cylinder for stable continuous molding. In particular, in the case of molded products that require insert metal and the like to be molded, the longer the time from the opening of the mold until the assembly, the easier the work, but if the thermal stability in the cylinder is insufficient, it will melt. In many cases, molding of phenol resin molding materials was not stable due to the progress of curing due to the thermal history of the cylinder. In particular, in the case of a molded product that is complicated and takes a long time to insert, conventionally, the curability is sacrificed and the mold temperature and the cylinder temperature have to be lowered to perform molding, which is a great limitation in terms of productivity.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a phenolic resin molding material for injection molding which is excellent in fluidity and thermal stability in a cylinder without impairing curability.

[0004]

According to the present invention, such an object is achieved by a phenol resin molding material containing a phenol resin in which 5 to 50% of phenolic hydroxyl groups are urethanized with an isocyanate compound. Hereinafter, the contents of the present invention will be described in detail.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION A phenol resin for urethanizing a phenolic hydroxyl group used in the present invention is a novolac type,
It may be either a resol type or a mixture of both. At this time, if the rate of urethanization is 5% or less, the effect of thermal stability in the cylinder is small, while if it exceeds 50%, curing in the mold is significantly delayed. The phenol resin in which the hydroxyl group is urethanized by 5 to 50% is blended so that the ratio of the urethane group and the phenolic hydroxyl group in the resin component is 5:95 to 40:60 in an equivalent ratio. At this time, if the proportion of urethane groups is less than 5 equivalent ratio, the effect of thermal stability in the cylinder is small, while if it exceeds 40 equivalent ratio, curing in the mold is significantly delayed.

The isocyanate compound for urethanizing the phenolic hydroxyl group used in the present invention is not particularly limited as long as it is a monoisocyanate compound. Non-limiting examples of these are ethyl, propyl, butyl isocyanate and the like. As a method for synthesizing a urethanated phenol resin, a phenol resin solution is dissolved in an organic solvent, a predetermined amount of an isocyanate compound is reacted at room temperature, and then the solvent is distilled off under reduced pressure. At this time, the reaction time can be shortened by using a reaction catalyst such as lead naphthenate.

The phenolic resin molding material of the present invention usually contains a filler. As the filler, normal wood powder,
Organic fillers such as pulp, cloth chips, polyvinyl alcohol fiber, acrylonitrile butadiene rubber, and inorganic fillers such as calcium carbonate, aluminum hydroxide, calcium hydroxide, silica, clay, mica, zeolite, talc, glass powder, glass fiber, etc. Is used. The content of the filler is preferably 30 to 250 parts by weight with respect to 100 parts by weight of the resin component. If it is less than 30 parts by weight, the properties such as dimensional stability may be inferior, and if it exceeds 250 parts by weight, the strength may decrease. In addition to the filler, an ordinary curing agent (eg hexamethylenetetramine), a co-curing agent (eg slaked lime), a release agent (eg zinc stearate), and if necessary, a coloring agent (eg carbon black), A surface treatment agent (for example, a silane coupling agent), a flame retardant (for example, boric acid), etc. can be added. This mixes the blend evenly, then rolls,
A phenol resin molding material is obtained by heating and kneading with a kneader, a twin-screw extruder, or the like, and granulating if necessary.

By converting the phenolic hydroxyl group into a urethane, the activation energy of the reaction of the phenol resin with hexamethylenetetramine and formalin is increased, and the temperature dependency of the reactivity is increased.
It is thermally stable before and after, and the curing reaction does not slow down at around 180 ° C. in the mold.

[0009]

EXAMPLES Examples are shown below to specifically illustrate the present invention. Unless otherwise specified, parts and% indicate parts by weight and% by weight.

(1) Production Example of Urethane Phenol Resin Production Example 1 103 parts of novolak resin having a number average molecular weight of 400 and a hydroxyl group equivalent of 103 and 100 parts of acetone are placed in a flask equipped with a stirrer and a dropping funnel and stirred at room temperature. While the novolak resin was dissolved. Next, after adding 1 part of lead naphthenate as a catalyst, 50 parts of butylisocyanate was gradually dropped from the dropping funnel and kept at the same temperature for about 1 hour to complete the reaction, and then acetone was distilled off under vacuum to remove hydroxyl group. Equivalent 290 (50% of phenolic hydroxyl groups converted to urethane)
The urethane-modified novolak resin of was obtained. Production Example 2 A urethane having a hydroxyl equivalent of 150 (urethane of 20% of phenolic hydroxyl groups) was produced in the same manner as in Production Example 1 except that 103 parts of a resol resin having a number average molecular weight of 600 and a hydroxyl equivalent of 103 and 20 parts of butyl isocyanate were used. A resol resin was obtained. Production Example 3 A urethane having a hydroxyl equivalent of 110 (4% of phenolic hydroxyl groups is urethanized) in the same manner as in Production Example 1 except that 104 parts of a novolak resin having a number average molecular weight of 700 and a hydroxyl equivalent of 104 and 4 parts of butyl isocyanate were used. A modified novolac resin was obtained.

Table 1 shows Examples 1 to 3 and Comparative Examples 1 to 4 using the urethanated phenolic resins shown in Production Examples 1 to 3.
After blending and uniformly mixing the respective components in accordance with the above, the mixture was kneaded with a hot roll, cooled, and pulverized to obtain a phenol resin molding material.

[0012]

[Table 1]

The following evaluations were performed on Examples 1 to 3 and Comparative Examples 1 to 4. 1) In-cylinder thermal stability In a cylinder, the material is weighed in a cylinder set to the conditions shown in Table 2, and left for a predetermined time with the cylinder nozzle touching the mold, and then molded to obtain a complete molded product. The longest retention time was measured. 2) Curability evaluation When injection molding was carried out under the conditions shown in Table 2, the minimum swelling disappearance curing time was measured until swelling due to uncuring did not occur on the surface of the molded product having a thickness of 5 mm. In addition, the minimum curing time required for disappearance of internal voids due to uncuring of a 15 mm square molded product was measured.

[0014]

[Table 2] Table 3 shows the evaluation results of Examples 1 to 3 and Comparative Examples 1 to 4.
Shown in

[0015]

[Table 3] As is clear from Table 3, it was confirmed that the phenol resin molding material of the present invention had excellent thermal stability in the cylinder.

[0016]

EFFECT OF THE INVENTION The phenol resin molding material of the present invention is particularly excellent in thermal stability in the cylinder and has no other adverse effects. Therefore, it has been a big limitation in application until now, long molding time, insert molding, It can be applied to hoop molding.

Claims (2)

[Claims] 1. A phenol resin molding material comprising a phenol resin in which 5 to 50% of phenolic hydroxyl groups are urethanized with an isocyanate compound. 2. The phenol resin molding material according to claim 1, wherein the ratio of the urethane group and the phenolic hydroxyl group in the resin component is 5:95 to 40:60 in an equivalent ratio.