JPH0141744B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing glass fiber mat.

Glass fiber mat is made by dropping short glass fibers produced by a centrifugal method, flame method, etc. onto a moving perforated conveyor, depositing them to a predetermined thickness to form a mat, and containing a thermosetting resin in between. It is manufactured by adding an aqueous binder, then heating to cure the resin, and bonding the short glass fibers together with the cured product.

Glass fiber mat has good sound absorption and heat insulation properties, and has excellent properties such as lower combustion and light weight, and is widely used as a sound absorbing material, a heat insulating material, an interior material, etc.

When manufacturing glass fiber mat, glass fiber mat to which an uncured aqueous binder has been added (hereinafter referred to as uncured mat) is heated to harden the thermosetting resin contained in the aqueous binder (hereinafter simply referred to as mat). It is necessary to harden the
This curing process has the following industrial technical difficulties.

Glass fiber mat is lightweight, has a high bulk density, and has great insulation properties. When heating an uncured glass fiber mat, it is difficult to transfer heat to the inside of the mat even if the surface of the mat is heated, and it takes a long time to heat the mat, and it is difficult to uniformly heat the entire mat. Therefore, productivity is low, and the resin inside the mat is often insufficiently cured or the resin on the surface is overheated.

For this purpose, the surface of the pine is held between a pair of caterpillar-shaped perforated metal plates, and high-temperature gas is introduced through the holes in one metal plate, and the high-temperature gas is introduced through the holes in the other metal plate. A widely used method is to heat the mat by passing hot gas through the mat by venting the gas. Although this method (hereinafter referred to as hot air circulation method) has high productivity and is an extremely suitable method from an industrial perspective, it has the following drawbacks.

(1) Since the uncured mat protrudes from the holes in the metal plate, it is impossible to obtain a mat with a flat surface.

(2) When trying to manufacture a pine with a high bulk density, the ventilation resistance of the pine is large, making it difficult to uniformly heat the inside of the pine.

(3) When a filler with high ventilation resistance is added to the mat, or when a moisture-proof layer such as kraft paper is attached to the mat, it becomes difficult to pass high-temperature gas through the mat. Therefore, when manufacturing a mat having a moisture-proof layer, it is necessary to first harden only the mat and then apply the moisture-proof layer using an adhesive.

Heating with high frequency waves directly heats the object to be heated to the inside, so it has the advantage of being able to uniformly heat objects with high insulation properties, that is, large thermal resistance.As far as this point is concerned, it is a suitable method for heating glass fiber mats. It is. However, heating glass fiber mats using high-frequency dielectric heating has the following drawbacks.

Objects placed in a high-frequency electric field self-heat due to molecular vibrations caused by the high-frequency waves, and the amount of heat generated is proportional to ε·tanδ (where ε is the dielectric constant and δ is the loss angle). Glass fiber mat is made by bonding glass fibers with a binder whose main component is a small amount of phenolic resin.
Since tan δ is small, especially ε and tan δ of glass fibers, the amount of heat generated is small, and direct heating by high frequency is not considered to be an industrially suitable method.

Heating glass fiber mats with high frequencies is described, for example, in U.S. Pat. The glass fiber mat is heated indirectly by this mold.

In order to solve the above-mentioned difficulties in curing the glass fiber mat, the inventor of the present invention has conducted various studies to solve the above- ^mentioned difficulties in curing the glass fiber mat. By passing it between a pair of high-frequency electrodes installed in parallel at a predetermined distance in a compressed state to a density of ^m3 or more, and heating it with dielectric heating between them, extremely favorable results can be obtained. I discovered that
This is proposed as the present invention.

As mentioned above, glass fiber mat is composed of glass fibers and a small amount of binder (several percent to 10-odd percent of the glass fibers), but uncured mat also contains
It contains about several percent to ten-odd percent of water relative to glass fiber. Since the ε and tan δ of water are much larger than those of glass and phenolic resin, which is the main component of the binder,
The uncured pine is rapidly heated between high frequency electrodes. The energy given to the pine by the high frequency is used as the latent heat of vaporization of water, and the temperature of the pine is maintained at 100℃ while the water is evaporating, and once the water evaporation is complete, the temperature of the pine is
The temperature rises above 100°C, but in this state, ε and tanδ are small and the amount of heat generated is small. Generally, in order to cure a phenolic resin, it is necessary to heat the phenolic resin to about 150°C. Therefore, in order to harden pine by high-frequency heating, it is necessary to perform heating in a region where ε and tanδ are small, and high-frequency heating has low productivity and is difficult to be considered industrially suitable. . However, according to the experimental results of the present inventors, it has been found that if the uncured mat is heated under the conditions described above, extremely favorable results can be obtained as described below.

(1) Even high-density pine can be cured uniformly in a short time.

(2) A pine with a smooth surface can be obtained.

(3) Mats with a moisture barrier layer can be manufactured in one step.

(4) There is no possibility of the binder being half-baked. The amount of binder in the uncured mat may be non-uniform, and in conventional methods, areas containing an excess of binder may be insufficiently cured, resulting in half-baked spots.

Although the reason why such favorable results are obtained is not clear, it is thought to be approximately as follows. Even if the temperature of the mat exceeds 100℃, a small amount of moisture remains in the binder, and the density of the mat remains relatively high, and since the mat is sandwiched and sealed between a pair of electrodes, water vapor remains,
ε・tanδ becomes larger than expected, dielectric loss mainly occurs in the binder part, the binder is effectively heated, and since the thermal conductivity of pine is low, heat is difficult to dissipate to the outside, and the binder It appears that curing occurs quickly.
In addition, the portion containing an excessive amount of binder has a high water content and the amount of heat generated in this portion is large, so that half-burning of the binder is less likely to occur.

Next, the present invention will be explained in more detail.

In the figure, 1 is a fixed electrode, 2 is a driving electrode, and both electrodes are respectively connected to a high frequency oscillator (not shown). The fixed electrode 1 is formed of a metal flat plate such as an aluminum plate, and the driving electrode 2 is formed of an elastic endless belt made of stainless steel or the like, and is moved parallel to the fixed electrode 1 in the direction of the arrow by a driving device (not shown). It is also moved at a predetermined speed at a predetermined distance from the fixed electrode 1, and is grounded by a suitable grounding device.

30Kg/m ³ or more, preferably 40Kg/m
An uncured glass fiber mat 5 compressed to a density of Kg/m ³ or more and having a hardened surface layer is supplied. As the uncured glass fiber mat 5, a binder mainly composed of phenolic resin is used as a fixed component for the glass fiber.
A water content of about 2 to 10 wt%, with a water content of about 2 to 10 wt%, can be suitably used.

The uncured glass fiber mat is uniformly cured in a short time of about 1 to 3 minutes, and a uniform mat with a smooth surface can be obtained.

Note that, as described above, since the glass fiber mat has a low thermal conductivity, the thermal energy generated by high frequency waves is difficult to dissipate to the outside. Since heat generated by high frequency waves is more easily dissipated from the surface of the mat than from the inside, heating of the surface is likely to be insufficient. For this reason, it is desirable to harden the mat surface in advance as described above.

Furthermore, instead of the aqueous binder containing uncured resin, an inorganic aqueous binder (for example, Hishicol, trade name, manufactured by Nihon Kagaku Kogyo Co., Ltd.) can also be used.

[Brief explanation of drawings]

The figure is a front view showing an embodiment of the method for manufacturing a glass fiber mat according to the present invention.

Claims (1)

[Claims] 1 Short glass fiber matte to which an aqueous binder has been added is compressed to a density of 30 kg/m ³ or more, and passed between a pair of high-frequency electrodes installed in parallel with a predetermined distance between them, during which dielectric heating is applied. 1. A method for producing glass fiber mat, characterized by heating it by heating.