JPH02284932A - Production of foamed phenolic resin - Google Patents

Abstract

PURPOSE:To obtain the subject foamed material useful as a heat-insulation material, cushioning material, panel, board, etc., by impregnating a liquid mixture containing a mixed phenolic resin consisting of novolak and resol, a solvent, a foaming agent and a foam stabilizer into a nonwoven fiber sheet substrate, drying the liquid and foaming the composition. CONSTITUTION:A liquid mixture containing (A) a mixed phenolic resin consisting of novolak and resol, (B) a solvent of said resin (preferably a volatile polar organic solvent having a boiling point of <=120 deg.C, e.g. methanol or acetone), (C) a foaming agent (e.g. N,N'-dinitrosopentamethylenetetramine) and (D) a foam stabilizer (preferably silicone compound) is impregnated in a nonwoven fiber sheet substrate, dried and foamed to obtain the objective foamed product. The mixing ratio of novolak:resol is preferably 90:10 to 70:80 by weight.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing phenolic resin foams useful for applications such as heat insulating materials, cushioning materials, panels, boards, and the like.

More specifically, the present invention involves dissolving or uniformly mixing a mixed phenolic resin consisting of novolac and resol in a solvent together with a blowing agent, hardening agent, foam stabilizer, etc., and impregnating a sheet-shaped nonwoven fiber base material with the solution. The present invention relates to a method for producing a high-strength phenolic resin foam, which is characterized in that by foaming after drying, the fibers are unraveled by internal pressure during foaming, so that the fibers are uniformly dispersed within the foam.

[Conventional technology]

Conventionally, in order to improve the mechanical strength of phenolic resin foam, it has been considered to mix various reinforcing fiber materials into the foam. The second method is to mix a foamable resin composition powder containing a condensate (raw material for phenolic resin foam) and foam and harden it in a mold. After being spread between the flocculent sheet materials, these are preformed using hot rolls, hot presses, etc. at a temperature that allows the initial condensate of the phenolic resin to melt for each resin composition, and the inside of each flocculent sheet is impregnated with the resin composition. A method of holding and heating this multilayer body to foam and harden it (Special Publications Publication No. 4
No. 7-8945), and the third method is to spread the powdered foamable resin composition solution between two or multiple laminated cotton-like sheets and then heat them at a low temperature to form individual cotton sheets. A method of impregnating and retaining a resin composition inside a shaped sheet and heating and foaming and curing this multilayer body (Japanese Patent Laid-Open No. 61-213
No. 528) is known.

[Problem to be solved by the invention]

However, in the first method, it was difficult to mix the fibers and the resin composition uniformly, and it was difficult to obtain a foam molded article in which the phenol resin foam layer and the fibers were uniformly mixed. In the second method, the sheet is impregnated at the lowest possible temperature at which the resin melts without foaming hardening, but because this temperature range is narrow, foaming hardening tends to occur locally, and the adhesion between the sheet and the resin is poor. There are also problems such as bad things. The third method also improves the above points, but since it uses a powdered resin composition, it is difficult to mix the foam stabilizer, resulting in poor foaming conditions, and it is difficult to add additives such as plasticizers. There were problems such as.

In view of this problem, some of the inventors of the present invention first impregnated a sheet-shaped nonwoven fiber base material with a novolac type phenolic resin dissolved in a solvent, dried it, and then foamed it, thereby combining the fibers with the phenolic resin. It has been discovered that a foamed composite body in which foam layers are uniformly mixed can be easily manufactured, and the invention has already been proposed.

However, this method had the inconvenience of unavoidably generating ammonia odor from hexamethylenetetramine used as a curing agent for novolac. [Means for Solving the Problem] As a result of further study, the present inventors found that By impregnating a sheet-shaped nonwoven fiber base material with a mixture of phenolic resin, which is a mixture of novolac and resol, dissolved in a solvent, the problem of the above-mentioned tool is solved, and the base material is removed during foaming. The present invention was achieved by discovering that the fibers of the material are dispersed and mixed uniformly within the foam.

That is, the present invention impregnates a sheet-shaped nonwoven fiber base material with a mixed liquid containing a mixed phenolic resin consisting of novolac and resol, a solvent in which the resin is soluble, a foaming agent, and a foam stabilizer, and then drying the mixture. This is a method for producing a phenolic resin foam characterized by foaming, and a vaporizable polar organic solvent with a boiling point of 120° C. or lower is used as a solvent in which novolak is soluble.

The phenolic resin used in the present invention is a novolak type and resol type phenolic resin, and according to a conventional method,
Almost all novolac-type resins can be used as long as they are made by reacting phenols and formaldehyde with an acidic or basic catalyst and are soluble in the solvents mentioned below or can be mixed uniformly by emulsification. Alternatively, resol type resin can be used. However, from the viewpoint of miscibility with novolak, solid or solvent-soluble resols are preferred.

In addition to phenol, the phenols that can be used in the present invention include alkylphenols such as cresols, xylenols, and octylphenols, and bisphenol A1.
Phenylphenols, phenols with alkylphenol-like structures such as styrenated phenols, alkenylphenols such as p-vinylphenol and isopropylphenols, etc. may be used alone or in combination of two or more, and as aldehydes. Formaldehyde, paraformaldehyde, acetaldehyde, furfural, etc. can be used.

An acidic catalyst is used as a catalyst for novolac production, and a basic catalyst is used as a catalyst for resol production, and a normal reaction is carried out to produce a novolak type or resol type phenol resin.

The mixing ratio of novolak and resol is not particularly limited, but from the viewpoint of the strength of the foam, novolak:resol-90 is used.
:10 to 70:30 (weight ratio) is preferable.

The solvent is one that dissolves the above mixed phenolic resin and is inert, and has a boiling point of 12, which easily vaporizes at room temperature.
A polar organic solvent is used at 0°C or lower.

As such solvents, lower alcohols such as methanol and ethanol, ketones such as acetone, nitriles such as acetonitrile, ethers, esters, amines, and aromatic compounds having polar groups can be used. be. Nonpolar hydrocarbons and many aromatic compounds cannot be used because they do not dissolve phenolic resins, and carboxylic acids tend to decompose blowing agents and harden the resol.

As the blowing agent, organic decomposition type blowing agents such as N,N'-dinitrosopentamethylenetetramine, benzenesulfonyl hydrazide, azobisisobutyronitrile, etc., and inorganic decomposition type blowing agents such as sodium bicarbonate and ammonium nitrite are used. However, organic decomposition type blowing agents are preferable from the viewpoint of miscibility with solvents.

As the foam stabilizer, common silicone-based, metal soap-based, and polymer-based foam stabilizers are used, but silicone-based foam stabilizers that are resistant to high temperatures are preferred. In addition, rubbers, polyvinyl alcohols, polyamides, etc. can be added as modifiers.

In the present invention, there is no need to use conventional curing agents since the resol acts as a curing agent for the novolak.

However, when production of a high-strength foam is required, hexamethylenetetramine, paraformaldehyde, etc. can be used, but these are not preferred from the viewpoint of odor.

As a method for producing a foam, first, a mixed phenolic resin is dissolved in a solvent, and a foaming agent, a foam stabilizer, and their geothermal additives are added and mixed uniformly. At this time, if you add the foaming agent and foam stabilizer last, they will mix well.

The concentration of the mixed phenolic resin is preferably 20% (% strain, the same applies hereinafter) or more, but from the viewpoint of workability, the viscosity of the solution should be 100-1.
It is desirable to set it to 0000 cps.

At this viscosity, even substances that are poorly soluble in the solvent can be mixed uniformly, and it is also easy to impregnate the base material.

The appropriate amount of blowing agent is added depending on the expansion ratio and the adhesion density of the blowing agent to the base material. If the amount of foaming agent is small, sufficient foaming will not occur and the shape and physical properties of the foam will be adversely affected.
On the other hand, if the amount of foaming agent is too large, the pressure inside the mold becomes too high during foaming, which may cause blowing out of the mold, which is dangerous. It is usually added in an amount of 1 to 10%. A foam stabilizer is also added as appropriate, but the amount is 1 to 1 per 100 parts of mixed phenolic resin.
Part O is preferred.

This mixed solution is impregnated into a sheet-like nonwoven fiber base material, and conventional methods such as impregnation and coating may be used, but it is necessary to impregnate the resin into the base material. At this time, it is desirable that the ratio of the mixed liquid to the base material be 2:8 to 9:1 of the mixed phenol resin base material.

Drying is preferably done by air drying at room temperature for about 48 hours. Drying by applying heat is also possible, but applying heat causes the blowing agent to decompose, which is not preferable. For air drying, hang the impregnated nonwoven fiber base material in a shaded and well-ventilated place or dry it on release paper to form a clean sheet. When applying heat, 1 to 2 at 40 to 70℃
Let dry for an hour.

The nonwoven fiber base material used in the present invention is a nonwoven fabric formed into a sheet of inorganic nonwoven fibers such as glass fiber, metal fiber, and carbon fiber, and organic nonwoven fibers such as cotton, recycled fiber, and synthetic fiber. A typical example is glass mat. The thickness and weight can be set arbitrarily.

Foaming of this sheet-like base material is carried out by loading the base material cut into an appropriate size into a mold and heating it. Although it is possible to use one or more base materials, the thickness of the base material may be limited by the heating device when the base material is made into multiple layers. The heating method may be a generally known method such as a heating press,
Anything can be used, such as infrared rays and a dryer. However, it is difficult to make molded products with a thickness of 801I11 or more using a press or other device that heats the surface of the mold. Heating temperature is 120-180
The optimum temperature is ℃, and foaming and curing takes place within several minutes to several tens of minutes.

[For production]

In the method of the present invention, since the resin is dissolved in the solvent, it is easy to mix additives, and it is easy to add foam stabilizers and plasticizers.
In addition, since the resin can be impregnated into the inside of the non-woven fiber base material, the binder of the non-woven fiber base material is peeled off by the foaming pressure during foaming, and the fibers are uniformly dispersed within the foam. , which gives the foamed composite high strength.

〔Example〕

Example 1 10 parts by weight of a 50% by weight methanol solution of novolak resin prepared using phenol and formaldehyde using an acid catalyst according to a conventional method, and 10 parts by weight of a solid resol prepared using a base catalyst using phenol and formaldehyde according to a conventional method. As a blowing agent, N,N'-dinitrosopentamethylenediamine (Celmic A: manufactured by Sankyo Kasei) 5
Part by weight, silicone oil (L-7002:
2 parts by weight (manufactured by Nippon Unica ■) were stirred with a mixer, and the mixed liquid was poured into a 25cm x 25cs glass mat (MC450).
A: Nittobo ■) was impregnated with dobu-zuke, lightly squeezed and air-dried in the shade. The amount of impregnation after drying is glass: resin-5
The ratio was 0:50, and the thickness was 1.5 mm. 1 to 6 of these sheets are 25cm x 25G! 1 X O, 8~
The mixture was placed in a 2 am mold and heated at 120° C. for 10 minutes to form a glass fiber-containing foam having the same shape as the mold. The glass fibers in this foam were almost uniformly dispersed. Strength etc. are as described in Table 1.

Example 2 A mixed solution prepared in the same manner as in Example 1 was placed in a 25 cm x 25
The nylon nonwoven fabric (to) was impregnated with a roller and air-dried in the shade. The amount of resin after drying is: Resin: Nonwoven Fabric-40: G
o, and the thickness was 1 inch. This sheet, 3 sheets 2
The mixture was placed in a mold of 5 cm x 25 cm x 2 (maximum) and heated at 150°C for 10 min to foam, yielding a foam having the same shape as the mold. The nonwoven fabric in the foam was almost uniformly dispersed.

Example 3 15 parts by weight of the resol used in Example 1, 6 parts by weight of a foaming agent, 3 parts by weight of a foam stabilizer, and 7.0 parts by weight of a foam stabilizer were added to 100 parts by weight of a 70 vL% methanol solution of novolac resin.
1/Near/I/ (PVA202; Made by Kuraray ■> 5
ffi amount was mixed and aluminum fiber nonwoven fabric (25cm x
25an) by hand lay-up method. The amount of resin after air drying was resin:nonwoven fabric-20:80.

This was placed in a 25cm x 25cm x O, 5CD+ mold and foamed and cured at 180°C for 12 minutes to obtain a foam having the same shape as the mold. The aluminum fibers in the foam were almost uniformly dispersed.

Comparative Example 1 For 100 parts by weight of the novolak resin used in Example 1,
Similarly, 10 parts by weight of the resol resin used in Example 1, 10 parts by weight of a foaming agent, and 2 parts by weight of a foam stabilizer were added, kneaded using heated rolls, and then crushed to obtain a powdered foamable resin composition. Sprinkle 55 g of this powder on the mat used in Example 1, and cover it with another mat to make a two-layer stack of 25 cm x
The mixture was placed in a 25CQI x 1 cm mold and foamed and cured at 150°C for 10 minutes to obtain a foam. However, this foam was difficult to handle because the powder moved when the resin composition was loaded, and the foam itself was non-uniform as it had cavities that were not filled with the phenol foam layer.

Comparative Example 2 The formulation of Comparative Example 1 was kneaded with a heating roll and then ground to obtain a powdered foamable resin composition.

Next, as a binder, a mixture of methyl alcohol (special grade reagent) and trichlorotrifluoroethane in a volume ratio of 1=5 was used, and 5 g of the mixture was sprayed onto the mat used in Example 1 in a mist form using a nozzle. 30g of the foamable resin composition was sprinkled on the mat that had absorbed the binder, and then a mat that had also absorbed the binder was placed on top of it, preformed under a pressure of about 1 kg, and then hot air circulated at 60°C. 10 in a tank
Dry for 0 minutes. Next, divide this sheet into 25cm x 2
The mixture was placed in a 5 cm x 1 cm mold and heated at 150° C. for IO minutes to form a foam. This foam had a poor foaming condition, no resin was attached to the glass layer on the surface, and the surface was uneven.

Table 1 shows the physical properties of the foams produced in Examples 1 to 3.

〔Effect of the invention〕

According to the present invention, since the resol acts as a curing agent, there is no problem of generation of ammonia odor during foam curing, and a foamed composite in which fibers and phenolic resin are evenly mixed can be efficiently and stably obtained. . Since this sheet-shaped foamed composite does not use heat during production, it is easily manufactured, and various additives can be mixed in, allowing various combinations to be used depending on the use of the composite.

Patent applicant: Showa Kobunshi Co., Ltd. teenager Reason Man

Claims (3)

[Claims] (1) Impregnating a sheet-shaped nonwoven fiber base material with a mixed liquid containing a mixed phenolic resin consisting of novolac and resol, a solvent in which the resin is soluble, a foaming agent, and a foam stabilizer, and foaming after drying. A method for producing a phenolic resin foam characterized by: (2) The phenolic resin foam according to claim 1, characterized in that a volatile polar organic solvent with a boiling point of 120°C or less is used as the solvent in which the mixed phenolic resin consisting of novolak and resol is soluble. manufacturing method. (3) The method for producing a phenolic resin foam according to claim 1 or 2, wherein the curing is carried out by self-crosslinking of the resol.