JPH0337499B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a highly foamed resin body. In general, synthetic resin foam has excellent performance as a heat insulating material, and is widely used in buildings, refrigerators, etc., and has become even more important as it meets the need for resource and energy conservation due to the recent oil shortage. Demand is expected. In addition, from the perspective of resource conservation, there is an increasing demand for foams with a high expansion ratio (low density foams) (hereinafter simply referred to as high foams). In particular, thermosetting resins that are water-soluble or water-dispersible (hereinafter referred to as hydrophilic thermosetting resins) can be foamed using air as a foam, and in this method, most of the time after discharge from a foaming machine is There is no volume expansion, and quality control is easy. There is a great demand for hydrophilic curable resins because they use air as a blowing agent and are therefore inexpensive to manufacture and have good workability. Conventionally, for example, a method for manufacturing urea resin foam is to blow air into a foaming liquid made of an acidic curing liquid containing a surfactant in a foaming machine to make it foamy, and then to add a urea resin initial condensate as the main ingredient. The so-called spray method, in which a resin liquid is sprayed and then discharged from a foaming machine, has been common. However, the nonvolatile content in this case is usually only increased to 20% by weight, and after foaming, water seeps out of the foam and contaminates other substrates, such as panels, and it takes a long time to dry. There were some important shortcomings. If the nonvolatile content was increased to reduce water content, voids would occur in the resulting foam, making it impossible to obtain a uniform foam. Therefore, since the nonvolatile content concentration at which water does not leach out is at least 30% by weight, urea resin foams using raw materials with such a high concentration are usually produced using a mixing machine called a mechanical floss foaming machine, rather than using a spray method. Mix resin raw materials, curing agent and air,
Air is uniformly dispersed in the resin to create a foamed state.
Attempts have been made to produce a foam by discharging it from a mechanical floss foaming machine and then allowing the foam to harden. However, according to this manufacturing method, as the expansion ratio increases, the foam-containing material discharged from the mechanical floss foaming machine tends to collapse before hardening. This is thought to be because as the expansion ratio increases, the thickness of the foam-containing material becomes thinner, and the foamed state cannot be maintained until curing is completed. In order to solve this phenomenon, it is necessary to shorten the curing time. However, in order to uniformly foam a large amount of air in a mechanical floss foaming machine and increase the foaming ratio, it is necessary to increase the residence time inside the mechanical floss foaming machine.
If the curing time is shortened, curing occurs within the foaming machine, making it impossible to operate, and a foam with a high expansion ratio cannot be obtained. As a result of extensive research, the inventor of the present invention limited the composition of the foam raw material and used a mechanical floss foaming machine as a mixer, thereby preventing hardening inside the foaming machine, preventing water seepage and voids. They discovered that it was possible to produce a highly foamed urea resin without the generation of urea resin, and filed a patent application (Japanese Patent Application No. 138604/1982). That is, the invention is directed to a resin foam with a non-volatile content of 30% by weight or more, consisting of 100 parts by weight of a resin liquid with a viscosity of 500 centipoise or less, which is mainly composed of a urea resin initial condensate, and 10 parts by weight or more of an acidic curing liquid with a pH of 2.5 to 1.0. The urea is characterized in that the foamed mixture is mechanically mixed and foamed using a mechanical floss foaming machine to form air bubbles, and then the resulting foamed mixture is discharged from the foaming machine and then hardened. The present invention relates to a method for manufacturing a resin foam. In the invention, a resin foam raw material and air are mechanically mixed and foamed using a mechanical floss foaming machine to form air bubbles, which are then taken out and hardened.
The resin liquid, which is one of the raw materials for the resin foam, is mainly composed of a urea resin initial condensate and has a viscosity of 500 centipoise or less. When the viscosity exceeds 500 centipoise, voids may be formed and a uniform foam may not be obtained. The urea resin initial condensate in the present invention is a water-soluble or water-dispersible reactant obtained by reacting urea and formaldehyde, and optionally contains melamine, dicyandiamide,
It is also possible to use compounds modified by reacting with at least one of compounds such as guanamine, benzoguanamine, and phenol, lower alcohols such as methanol and ethanol, ketones such as acetone, and aldehydes such as acetaldehyde and glyoxal. Additionally, additives such as methanol, ethanol, ethylene glycol, etc. may be included in order to improve the storage stability of the urea resin initial condensate and the cleanability of foaming equipment. Commercially available products such as Euroid #120 and Euroform R-101 (both manufactured by Mitsui Toatsu Chemical Co., Ltd.) can be used. The acidic curing liquid, which is one of the raw materials for other resin foams, is
PH is 2.5-1.0, preferably 1.7-1.2. If it exceeds 1.7, voids may occur in the foam, and if it exceeds 2.5, the foam may collapse before curing and the foam may not be formed. Further, if it is less than 1.0, partial hardening occurs in the foaming machine and operation becomes impossible, so it is particularly desirable to set it to 1.2 or more when long-term operation is required. Examples of this acidic curing liquid include:
Hydrochloric acid, sulfuric acid, phosphoric acid, oxalic acid, para-toluenesulfonic acid, their salts, aqueous solutions of acid anhydrides, etc. are used, and the amount is usually 10 parts by weight or more, preferably 20 parts by weight or more per 100 parts by weight of the resin liquid. use Further, it is preferable to add a surfactant to the resin liquid and/or the curing liquid. Examples of the surfactant include anionic surfactants such as ammonium lauryl sulfate, sodium higher alcohol sulfate, sodium alkyl diphenyl ether disulfonate, and sodium dodecylbenzenesulfonate in an amount of 0.2 to 5% by weight based on the total amount of foam raw materials;
Usually, when used in an amount of about 1 to 3% by weight, it is particularly effective in stabilizing bubbles. Other commonly used additives, such as foam stability and viscosity modifiers such as polyvinyl alcohol and carboxymethyl cellulose (CMC), urea and resorcinol, which have a formaldehyde-capturing effect, may also be included in small amounts in the resin foam raw material. The resin foam raw material has a nonvolatile content of 30% by weight or more, preferably 35 to 60% by weight, in order to avoid moisture seepage. If it exceeds 60% by weight, voids will be formed in the foam and the foam will have a high density, which is economically disadvantageous. A mechanical floss foaming machine is particularly preferred as a mixer that mixes the resin foam raw material and air to form bubbles. For example, as shown in FIG. 1, a rotor 4 having a large number of blades (protrusions) 3 rotates in a cylindrical container having a large number of protrusions 2 on the inner wall, and the blades 3 move between the protrusions without contacting the protrusions 2. Rotor 4
A mechanical floss foaming machine having a structure that rotates with the rotation of the foaming machine, a so-called pin mixer, a Hobart type batch mixer, an Oakes type continuous mixer (Japanese Patent Publication No. 17143/1973), etc. can be used. The above invention has been explained above, but in carrying out the above invention, when injecting the resin foam raw material, each component of the main resin (resin liquid), curing agent, and foaming air is injected through an injection port provided around the shaft. When injecting the hardener, the shaft part, especially the inlet part of the curing agent, becomes severely clogged, resulting in changes in the composition ratio, contamination of gelled substances, reduction in expansion ratio, and reduction in yield, resulting in unstable manufacturing and quality. There were concerns. This is thought to be because there is almost no mixing between the raw materials at the injection port of the resin foam raw material, so that an excess of curing agent occurs in some parts, resulting in partial curing.
By lowering the acid concentration of the curing agent and slowing down the curing speed, it is possible to suppress partial curing and reduce the clogging phenomenon even if an excessive curing agent occurs, but in this case, the foam-containing mixture will not foam. After the foam is discharged from the machine, the foam may collapse before it hardens, and a foam may not be formed. In order to avoid the above-mentioned troubles, it has been strongly desired to improve the method for producing more stable foams. In order to prevent the above-mentioned partial excess of the curing agent and obtain a uniform foam, the present inventor conducted various studies on the injection method of the resin foam raw material, and preliminarily mixed the curing agent and air. When mixed and injected with other resin foam raw materials through a separate injection port, a foam with stable quality such as density without contamination of gelled substances can be obtained, and the size of the cells in the obtained foam can be reduced. The present invention has been completed by achieving the unexpected results of a significantly improved heat insulating property with a smaller value. That is, the present invention involves mechanically mixing and foaming a resin foam raw material and air using a mechanical floss foaming machine to form air bubbles, and then discharging the resulting foam-containing mixture from the foaming machine. The method for producing a highly foamed material to be cured is characterized in that a curing agent, which is one of the raw materials for the resin foam, and air are mixed in advance and supplied. This will be explained with reference to the drawings. FIG. 1 is a sectional view of the mechanical floss foaming machine used in carrying out the above invention, in which a rotor 4 having a large number of blades (protrusions) 3 moves inside a cylindrical container having a large number of protrusions 2 on the inner wall. The blades 3 rotate between the protrusions together with the rotation of the rotor 4 without contacting the protrusions 2. Conventionally, each of the resin foam raw materials had injection ports A,
They are injected separately from B and C, and are mechanically mixed and foamed between the blades 3 and the protrusions 2 to form a foamed state. At this time, an excess of curing agent occurs near the injection port, causing trouble. In contrast, the present invention alleviates the partial excess state of the curing agent by pre-mixing the curing agent and air, and also helps the mixing inside the mechanical floss foaming machine to create a uniform and dense foam. I was able to obtain a foam. As a means of premixing, in particular methods using bead columns or spray nozzle tips give good results. FIG. 2 is a longitudinal sectional view illustrating a premixing method using a bead tower. In FIG. 2, air and curing agent are introduced into the shell 9 through nozzles 6 and 7, respectively.
The mixture of air and curing agent is mixed when passing through the perforated plate 11 and then the filling layer 10.
1' and is led to a mechanical floss foaming machine shown in FIG. 1 from a nozzle 8. Specific examples of the filling layer 10 include glass particles, plastic particles, etc., and the shapes of these particles are not particularly limited. FIG. 3 is a longitudinal sectional view illustrating a method using a spray nozzle chip, in which a spray nozzle chip 12, instead of a packed layer in a bead tower, is used.
12' is replaced by collision of high-speed spray streams. Regarding the spray nozzle tip shape,
It is not particularly limited as long as it has a shape that allows a spray stream to be obtained. The method of the present invention has been explained using urea resin foam, which is a typical resin foam, as an example, but is not limited to this. It can also be used for resin foams and the like. The present invention will be explained in more detail below with reference to Examples. Parts or percentages refer to parts or percentages by weight unless otherwise specified. Reference Example The urea resin initial condensate used in the Examples and Comparative Examples was produced as follows. 230 parts of urea, 36%
After mixing 620 parts of formalin and 30 parts of glycerin to make it homogeneous, adjust the pH of the solution to 7-9 and bring it to 90-90.
The reaction was carried out at a temperature of 100°C. After further adjusting the pH to 3.8 to 5.0 and continuing the reaction for 2 hours, 99 parts of urea was added and dissolved, followed by neutralization. The obtained urea resin initial condensate was concentrated under reduced pressure to a viscosity of 550 centipoise,
A urea resin initial condensate with a nonvolatile content of 68% was obtained. 35 parts of water per 100 parts of this urea resin initial condensate;
Two parts of sodium alkyl diphenyl ether disulfonate were added and mixed to prepare a resin liquid with a viscosity of 50 centipoise. PH containing 1.2% phosphoric acid and 1.0% sodium alkyl diphenyl ether disulfonate as curing liquid
An aqueous solution of 1.6 was used. Comparative Example A commercially available mechanical floss foaming machine of the type shown in Figure 1 (manufactured by Toho Kikai Kogyo Co., Ltd., Toho TM-302 model;
A rotor 4 has a large number of protrusions 2 on the inner wall of the cylindrical container, and has a large number of stirring blades 3 (protruding).
(a structure that rotates in close proximity to the protrusion 2 in the container),
The resin liquid prepared earlier is poured into the injection port A, and the curing liquid is poured into the injection port B at a weight ratio of resin liquid and curing liquid of 100/38.
In addition, compressed air was continuously injected from the injection port C to maintain the internal pressure in the foaming machine at 3.5 to 4.5Kg/ ^cm2 , and the rotor 4 of the foaming machine was rotated at a rotation speed of 450 RPM. It rotated. After the discharge through the discharge port 5 of the foaming machine and the injection hose (not shown) became stable, the foam-containing mixture was cured in a 30 cm square cardboard box. Table 1 shows the properties, density after drying, and thermal conductivity of the foam obtained. Also shown are changes in foam properties, density, and degree of clogging of the foaming machine due to continuous operation.

[Table] Example 1 The mixture outlet 8 of the bead tower in FIG.
Connect to hardening inlet B of the mechanical floss foaming machine shown in the figure. At this time, the injection port C is closed with a blind screw. The curing liquid is injected through the inlet 7 in FIG. 2, compressed air is injected through the inlet 6, and the mixture is injected into the mixture outlet 8.
The resulting mixture of curing liquid and air and the resin liquid injected from injection port A were mixed and foamed in a mechanical floss foaming machine to obtain a foam-containing mixture.
The liquid flow rate ratio and the operating conditions of the mechanical froth foaming machine were the same as in the comparative example. The results are shown in Table 1. Example 2 The bead tower of Example 1 was carried out in the same manner as in Example 1 except that the method using the spray nozzle tip shown in FIG. 3 was changed. The results are shown in Table 1. As described in detail above, the present invention is a method for easily producing a highly foamed resin body using an inexpensive gas, is advantageous in terms of energy saving and workability, and is extremely valuable in the production of heat insulating materials. It is an invention.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an apparatus for schematically explaining a conventional method. FIG. 2 is a longitudinal sectional view for explaining the method using a bead tower and FIG. 3 is a method using a spray nozzle tip. A, B, C... Inlet, 1... Foaming machine, 2...
Protrusion, 3... Stirring blade or protrusion, 4... Rotor,
5...Discharge port, 6...Air inlet, 7...Curing agent inlet, 8...Mixture outlet, 9...Ciel, 10
... (beads) packed bed, 11 and 11'... perforated plate, 12 and 12'... spray nozzle tip.

Claims (1)

[Scope of Claims] 1. 100 parts by weight of a resin liquid containing a urea resin initial condensate and having a viscosity of 500 centipoise or less, and a pH of 2.5.
A resin foam raw material with a non-volatile content of 30% by weight or more consisting of 10 parts by weight or more of an acidic curing liquid of ~1.0 and air is mechanically mixed and foamed using a mechanical floss foaming machine to form air bubbles. In a method for producing a highly foamed product in which a foam-containing mixture is discharged from the foaming machine and then cured, a curing agent, which is one of the raw materials for the resin foam, and air are premixed in advance to form the remaining resin foam. A method for producing a highly foamed material, characterized in that the material is supplied to a mechanical floss foaming machine through an injection port separate from the raw material. 2. The manufacturing method according to claim 1, wherein pre-mixing is performed using a spray nozzle tip. 3. The manufacturing method according to claim 1, which comprises premixing using a bead tower.