JPH0345702B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a novolak type phenolic resin foam molded article, and in particular, a method for producing so-called primary foamed particles in which a novolak type phenolic resin is partially foamed and hardened, and then molding. This invention relates to a method for producing a novolak-type phenolic resin foam molded article.

Conventionally, thermoplastic resins such as polystyrene resins, polyolefin resins, and copolymer resins thereof are known as primary foam particles having secondary foamability of plastic resins. However, as far as the inventors of the present invention know, such primary foam particles are not known for thermosetting resins. This is because thermosetting resins are generally heated and cured at the same time as foaming to maintain the foamed shape and obtain a foam. This is considered to be because it is technically difficult to stop the foaming in a partially foamed state, and it is not economically advantageous. Furthermore, it is not known to uniformly mass-produce foamed beads of thermosetting resin foam.

On the other hand, if you try to obtain a large green body or a molded body with a complicated shape from powder or granules without making them into primary foamed granules, the voids in the mold will be large compared to the amount of powder or granules filled. Therefore, the foam density tends to vary between above and below the void. On the other hand, molds with narrow voids have the disadvantage that foam filling tends to be uneven.

Under these circumstances, we focused on the fact that among thermosetting resins, novolac-type phenolic resin initial condensates are mainly powders, and as a result of various studies, we found that primary condensates of thermosetting resins with secondary foamability They succeeded in easily producing foamed beads, and discovered that the foamed beads were thermally fused to each other during secondary foaming during molding, leading to the completion of this invention.

Thus, according to the present invention, a novolak-type phenolic resin foam having secondary foaming properties is obtained by partially foaming and curing a composition comprising a novolak-type phenolic resin initial condensate and a required amount of a decomposable blowing agent and a curing agent. Production of a novolak-type phenolic resin foam molded article, which is characterized in that a novolak-type phenolic resin foam molded article is obtained by forming particles, then secondary foaming them in a mold, and molding the foamed particles while thermally fusing them to each other. law is provided.

The novolak type phenolic resin initial condensate, which is the main raw material of this invention, is a so-called novolak type phenolic resin known in the art, which is obtained by reacting phenols and aldehydes in the presence of an acidic catalyst, and is cured. It means that polymerization can proceed further in the presence of the agent. What are phenols?
In addition to phenol, 3,5-xylenol, m-
Cresol, 2,5-xylenol, 3,4-xylenol, 2,4-xylenol, 0-cresol, p-cresol and the like are included. Furthermore, examples of aldehydes include formaldehyde, paraformaldehyde, acetaldehyde, hexamethylenetetramine, and furfural.

These resins are in powder form at room temperature. A preferred precondensate for use in this invention is a condensate of phenol and formaldehyde.

The decomposable blowing agent in this invention means inorganic and organic blowing agents that can be decomposed by heating to generate gas. Typical examples of these are N, N'-
Organic decomposable blowing agents such as dinitrosopentamethylenetetramine, benzenesulfonylhydrazide, azobisisobutyronitrile, azodicarbonamide, paratoluenesulfonylhydrazide, as well as sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, ammonium nitrite, and azide compounds Examples include inorganic decomposition type blowing agents such as (eg CaN ₆ ). All of these are in powder form.

The curing agent used in this invention means a compound that can be decomposed by heating and can undergo a crosslinking reaction with the novolak type phenolic resin initial condensate. Such compounds include, like formaldehyde, compounds that are used to form phenolic resins by reaction with phenols, and are usually in powder form. Specific examples include hexamethylenetetramine, paraformaldehyde, methylal, dioxolane, trioxane, tetraoxane, trimethylolphosphine, S-triazine, and the like.

The amount of blowing agent added is determined mainly by considering the desired density of the final foam;
1 to 50 parts by weight per 100 parts by weight is appropriate, and 4
~8 parts by weight is preferred.

The amount of the curing agent added is generally 1 to 30 parts by weight, preferably 4 to 15 parts by weight, per 100 parts by weight of the resin.

The composition constituting the expanded granules of the present invention may contain small amounts of other various additives, such as fillers such as clay. These fillers are resin 100
It is preferable that the amount is 50 parts by weight or less.

It is generally preferable to granulate the above composition before partially foaming and curing it. For granulation, for example, a novolak-type phenolic resin initial condensate is
Melt at a temperature of ~90℃, add the required amount of blowing agent and required amount of hardening agent, and add fillers (clay, talc, zinc oxide, calcium carbonate, etc.) if desired, to make it as uniform as possible. It can also be carried out by mixing, then solidifying, and pulverizing to an appropriate size. A mixture of the above raw materials may be softened and melted at about 100° C. for a short time, solidified, and then pulverized. The size of the crushed grains is 5 to 10
An example is one that passes through a mesh.

The composition thus obtained is softened and melted by heating, shaped into a sphere by the surface tension of the composition, and partially foamed and hardened. This process involves forming a layer of a non-compatible, thermally stable, flowable powder material at the bottom of a suitable foaming mold, on or in which layer the granulated composition is added. This is done by placing or mixing an appropriate amount of In this state, if the composition is heated to an appropriate temperature while being shaken or rolled as necessary, the composition will not fuse with each other, and it is possible to obtain foamed beads that are independent and more spherical. It is presumed that this is achieved because the surface tension of the melt of the resin composition is greater than the surface tension of the non-compatible and thermally stable powder material. This means that
This is a new finding discovered by the inventors. Incompatibility here means that the composition does not substantially cause a chemical reaction with the composition and does not get wet easily (substantially does not get wet) with the composition during placement or mixing and during heat molding.
It means having physical properties. More specifically,
Suitable materials are those that do not substantially melt or react in the composition when placed, mixed or softened by heating, and have a surface tension lower than that of the liquid composition.

The term "thermally stable" means that physical changes such as softening or melting do not occur substantially at the molding temperature of the composition.

As such powder, various substances can be used, whether organic or inorganic, but inorganic powder is usually preferable, and specific examples thereof include clay,
Examples include talc, zinc oxide, calcium carbonate, calcium sulfate, carbon black, aluminum oxide, magnesium oxide, lead oxide, and the like. However, in addition to these, powders of fluorine-based and silicon-based organic polymer compounds are also mentioned as preferred examples. Note that a mixture (in powder form or irregular shape) of a novolak type phenolic resin initial condensate, a foaming agent, and a curing agent may be used in the above treatment without granulation.

The particle size of the powder material is suitably 0.005 to 2000 μm, preferably 5 to 1000 μm. The amount of the thermally stable powder that has no affinity for the resin composition must be such that the particles of the resin composition do not fuse together when melted. For example, the amount is preferably equal to or greater than the weight of the composition. The temperature and time at which this resin composition is partially foamed and cured are determined by taking into account the melting point (or softening point) of the novolak-type phenolic resin initial condensate in the resin composition and the amounts of the foaming agent and curing agent added. It should be determined by From another point of view, the primary foamed grains have a hardening degree of 1 to 99%, preferably 10 to 50%, and the treatment temperature is adjusted such that the residual amount of the blowing agent is 1% or more, preferably 10% or more. Time should be adjusted.

Here, the degree of hardening of the primary foamed grains is the weight percent of the ethanol-soluble content obtained by pulverizing the primary foamed grains and immersing them in ethanol. Examples of these appropriate values are specifically shown in the examples, and are appropriately selected and adopted with reference to the examples.

The primary foam beads of the present invention usually have a spherical shape or a similar shape, and the diameter ranges from about 1 mm to 20 mm.
Some are about millimeters in size. However, this size is
It is not particularly limited.

The primary foam particles are filled into a mold or the like having the desired shape depending on the intended use, and foam molding is carried out by a conventional method. The mold material should not melt, break, or deform due to the temperature during molding (usually 90°C or higher) and the foaming pressure, and should also be a closed type that allows the air inside the mold to be exhausted. Needless to say. The amount filled into the mold is 25% or more, preferably 70% or more in terms of bulk filling rate. Molding temperature is usually 90℃~170℃,
The molding time is determined in relation to the temperature, but is usually within 1 hour.

The foam molded product obtained in this manner by taking advantage of the secondary foaming characteristics of the phenol foam particles of the present invention can be easily produced with a uniform foam density for large molded products or molds with complex shapes. can get. The final foamed molded product can be up to about 60 times larger. In addition, in the obtained foamed molded product, the foam particles are strongly bonded to each other by heat, and the fractures rarely occur along the bonded surfaces, but span the cross section of each foam particle.

Next, the present invention will be described with reference to Examples, but the present invention is not limited thereto.

Example 1 A powdered resin mixture was prepared by adding 5 parts by weight of a blowing agent dinitrosopentamethylenetetramine and 10 parts by weight of a hardening agent hexamethylenetetramine to 100 parts by weight of a novolac type phenol-formaldehyde resin powder. In addition, this resin composition
The powder had a 100 mesh residue of 0.5%, the melting point was 81°C, and the gelation time at 150°C was 76 seconds. Then,
This resin mixture powder was softened and melted on a hot water bath at 100°C, then cooled and solidified, and pulverized to a particle size of 7 to 9 mesh to obtain a granular resin composition.

30 g of this granular resin mixture was placed on an approximately 1000 cm ² layer of calcined gypsum powder with a thickness of 2 to 3 mm, and foamed and hardened in a hot air circulation thermostat at 120° C. for 10 minutes to obtain foamed granules.

The obtained foamed particles were yellow in color, had a skin on the particle surface, had a dense cell structure, were spherical with a particle size of 2.5 to 4.5 mm, and had a bulk specific gravity of 0.21. Incidentally, 1.0 g of this foamed granule was pulverized and immersed in 20 ml of ethyl alcohol (reagent grade) at 25°C for 20 hours.
As a result of measuring the ethyl alcohol soluble content by
It was 88.3% by weight.

Next, the obtained foamed particles are made into particles with a particle size of 3.0 to 4.0 mm.
Sieve and fill 100% of the volume into a wooden mold.
The lid was closed and the mixture was kept in a hot air circulation constant temperature bath at 160°C for 45 minutes. The mold was removed from the thermostatic oven and the foam was removed from the mold.

The obtained foam is made by further foaming the primary spherical foam particles, and all the voids are filled with the foam layer, and the fusion between the primary foam beads is also very good, and it has a slightly brownish color. The molded product had a dense cell structure with a specific gravity of 0.21.

Example 2 The same resin mixture as in Example 1 was prepared into 7 to 9 mesh resin mixture granules using the same recipe.

This granular resin mixture was placed on a mold lined with calcined gypsum powder, and placed in a hot air circulation thermostat at 120°C.
The mixture was foamed and cured for 30 minutes to obtain foamed beads.

The foamed granules obtained are yellow in color and have a skin on the surface.
The particles were spherical with a particle size of 3.5 to 6.0 mm and had a dense cell structure, and a bulk specific gravity of 0.076. Further, the ethyl alcohol soluble content, which was determined by pulverizing the bubble particles and immersing them in ethyl alcohol, was 44.7% by weight.

Next, the particle size of the obtained expanded particles is 3.0 to 4.0 mm.
Sieve and fill 100% of the volume into a wooden mold.
The lid was closed and the mixture was kept in a hot air circulation constant temperature bath at 160°C for 45 minutes. The mold was removed from the thermostatic oven and the foam was removed from the mold.

The obtained foam is a product in which the primary spherical foam is further foamed, and all the voids are filled with the foam layer, and the fusion between the primary foamed spheres is also very good, and it has a slightly brownish color. The molded product had a dense cell structure with a specific gravity of 0.076.

Example 3 The same resin mixture as in Example 1 was prepared into 7 to 9 mesh resin mixture granules using the same recipe.

This granular resin mixture was placed on a mold lined with calcined gypsum powder, and placed in a hot air circulation constant temperature bath at 140℃ for 10 minutes.
The mixture was foamed and cured for a minute to obtain expanded beads.

The foamed granules obtained are yellow in color and have a skin on the surface.
The particles were spherical with a particle size of 3.5 to 5.2 mm and had a dense cell structure, and a bulk specific gravity of 0.070. Further, the ethyl alcohol soluble content, which was determined by pulverizing the expanded particles and immersing them in ethyl alcohol, was 52.0% by weight.

Next, the resulting foamed particles were sieved to a particle size of 3.0 to 4.0 mm, filled 100% of the bulk volume into a wooden mold, closed with a lid, and held in a hot air circulation constant temperature bath at 160° C. for 45 minutes. The mold was removed from the thermostatic oven and the foam was removed from the mold.

In this obtained foam, the primary spherical foam was further foamed, and 83% of the voids were filled with the foam layer, and the fusion between the primary foamed spheres was also extremely good. It was a brownish molded product having a dense cell structure with a bulk specific gravity of 0.070.

Example 4 The same resin mixture as in Example 1 was prepared into 7 to 9 mesh resin mixture granules using the same recipe.

This granular resin mixture was placed on a mold lined with calcined gypsum powder, and placed in a hot air circulation constant temperature bath at 130℃ for 20 minutes.
The mixture was foamed and cured for a minute to obtain expanded beads.

The foamed granules obtained are yellow in color and have a skin on the surface.
The particles were spherical with a particle size of 3.5 to 6.5 mm and had a dense cell structure, and a bulk specific gravity of 0.066. Further, the ethyl alcohol soluble content, which was determined by pulverizing the bubble particles and immersing them in ethyl alcohol, was 49.2% by weight.

Next, the particle size of the obtained expanded particles is 3.0 to 4.0 mm.
Sieve and fill 100% of the volume into a wooden mold.
The lid was closed and the mixture was kept in a hot air circulation constant temperature bath at 160°C for 45 minutes. The mold was removed from the thermostatic oven and the foam was removed from the mold.

In this obtained foam, the primary spherical foam is further foamed, and 70% of the voids are filled with a foam layer, and the fusion between the primary foamed spheres is also very good. It was a brownish molded product having a dense cell structure with a bulk specific gravity of 0.066.

Example 5 The same resin mixture as in Example 1 was prepared into 7 to 9 mesh resin mixture granules using the same recipe.

This granular resin mixture was placed on a mold lined with calcined gypsum powder, and placed in a hot air circulation constant temperature bath at 160℃ for 10 minutes.
The mixture was foamed and cured for a minute to obtain expanded beads.

The obtained foamed particles have a young brownish color, have a skin on the surface, and have a dense cell structure with a particle size of 4.5 to 6.5.
It had a spherical shape with a bulk specific gravity of 0.052.
In addition, the ethyl alcohol soluble content was determined by pulverizing this foam and immersing it in ethyl alcohol.
It was 9.6% by weight.

Next, the particle size of the obtained expanded particles is 3.0 to 4.0 mm.
Sieve and fill 100% of the volume into a wooden mold.
The lid was closed and the mixture was kept in a hot air circulation constant temperature bath at 160°C for 45 minutes. The mold was removed from the thermostatic oven and the foam was removed from the mold.

The resulting foam is a slightly brown color in which the primary spherical foam is further expanded and 23% of the voids are filled with a foam layer, with dots fused between the primary foam spheres. The molded product had a dense cell structure with a specific gravity of 0.052 and was flavorful.

Example 6 The same resin mixture as in Example 1 was prepared into 7 to 9 mesh resin mixture granules using the same recipe.

This granular resin mixture was placed on a mold lined with calcined gypsum powder, and placed in a hot air circulation constant temperature bath at 160℃ for 30 minutes.
The mixture was foamed and cured for a minute to obtain expanded beads.

The foamed granules obtained are yellow in color and have a skin on the surface.
The particles were spherical with a particle size of 5.0 to 7.0 mm and had a dense cell structure, and a bulk specific gravity of 0.044. Further, the ethyl alcohol soluble content, which was determined by pulverizing the bubble particles and immersing them in ethyl alcohol, was 1.2% by weight.

Next, the particle size of the obtained expanded particles is 3.0 to 4.0 mm.
Sieve and fill 100% of the volume into a wooden mold.
The lid was closed and the mixture was kept in a hot air circulation constant temperature bath at 160°C for 45 minutes. The mold was removed from the thermostatic oven and the foam was removed from the mold.

Although the obtained foam had little foamability and the foamed particles were not completely fused, a reasonable molded product was obtained.

Claims (1)

[Claims] 1. Novolak type phenolic resin foaming having secondary foamability by partially foaming and curing a composition comprising a novolak type phenolic resin initial condensate and required amounts of a decomposable blowing agent and a curing agent. Production of a novolak-type phenolic resin foam molded article, which is characterized in that a novolak-type phenolic resin foam molded article is obtained by forming particles, then secondary foaming them in a mold, and molding the foamed particles while thermally fusing them to each other. Law. 2. The manufacturing method according to claim 1, wherein the composition is granulated before being partially foamed and cured.