JPS6040377B2 - Flexible foam with skin and method for manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a skinned flexible foam and a method for manufacturing the same.

Conventionally, a two-component reactive urethane paint is known as a skin composition of a flexible foam with a skin that can provide a skin with excellent chemical resistance, but the skin obtained from this paint is generally It has drawbacks such as low elongation, insufficient flexibility, poor light resistance and heat resistance, large drop in elongation after aging test, and large discoloration.

Increasing the reactivity of a two-component reactive urethane paint has the disadvantage of shortening its shelf life (or lack of storage stability), while lowering the reactivity increases the curing time and reduces the number of molds required for molding. There is a disadvantage that the number increases and the cost increases. Also, one-component urethane paint, which is made by dissolving a linear urethane polymer in an organic solvent, is known as a paint that has good workability and productivity and provides a highly flexible skin. Naturally, it has disadvantages such as poor solvent resistance, poor chemical resistance, and poor retention of physical properties after light resistance test. As a method to improve the above-mentioned drawbacks, there is a method (measure a) of increasing the molecular weight of the linear urethane polymer and improving the chemical resistance by increasing the entanglement between molecules.
In this method, the effect of improving chemical resistance was insufficient, and moreover, there was a lot of stringiness during spraying of the paint, and in order to obtain a good skin, the non-volatile content (NV value) of the paint had to be significantly lowered. The second method is to use isocyanate as a constituent component of the linear urethane polymer, for example, to make it highly resistant to chemicals (Countermeasure 2), but the resulting skin shows yellowing after light and heat resistance tests. In addition, as a paint, it is necessary to use dimethylformamide (DMF), which has a strong dissolving power and is suitable for the human body, which has the disadvantages of poor working environment, slow evaporation rate, and long drying time. be. As a third method, 2
There is a method (measure c) of crosslinking linear urethane polymers with functional or polyfunctional active isocyanates, but since the solvent for linear urethane polymers generally contains an alcohol-based solvent, the -OH group* of the solvent It has the disadvantage that it reacts with isocyanate, shortening the expedient time and making it difficult to use. In order to avoid this drawback, if a non-alcoholic solvent is used, it is necessary to use DM, which results in the same drawbacks as mentioned above. Furthermore, active isocyanates are very harmful to workers and have disadvantages in productivity, such as creating a poor working environment. The above is summarized in Table 1. Note 1 in Table 1: Low indicates the case where the reactivity is lowered.

Note 2: High indicates the case where reactivity is increased.

Note 3 Judgment criteria: ○ Good, △ Good, × Bad.

The present invention is intended to solve the above-mentioned conventional drawbacks, and is to provide a skinned flexible foam that has good workability and productivity, and is excellent in chemical resistance and aging resistance, and a method for producing the same. The present invention uses a conventional one-component linear polyurethane paint mixed with blocked isocyanate as a skin material. A primary dry film is obtained using the one-component linear polyurethane, and then a predetermined foaming process is carried out. After the drying, the foam with the primary dry film is removed from the foaming mold, and the foam is then heated to cause the blocked isocyanate in the dry film to react and completely purify, thereby improving chemical resistance and aging resistance. It is characterized by obtaining a foam with a skin having the following properties.

The one-component urethane lacquer used in the present invention is one in which a thermoplastic urethane elastomer (linear urethane polymer) having a weight average molecular weight of 10,000 to 100,000 is dissolved in a solvent. In addition, the blocked isocyanate used in the present invention includes those having a difunctional to polyfunctional blocking agent (capping agent) dissociation temperature of 50 to 200q○, for example, about 13,000 or more and having the following formula: C2QC (CH2NHCOOC6 days 4CH3N
HCOOC6 days 5) 3 → C2 days 5C (CH2NHCOO
Phenol, which is a blocking agent, is dissociated and active isocyanate is regenerated according to the reaction formula expressed by C6QCday3NCO)313C6MrOH.

The amount of blocked isocyanate added is preferably 1 to 25 parts by weight per 10 parts by weight of the thermoplastic urethane elastomer. Next, the heat treatment conditions of the present invention are not particularly limited since the dissociation temperature varies depending on the blocked isocyanate used, and this dissociation temperature can be lowered by adding a dissociation catalyst. Furthermore, in the present invention, the blocked isocyanate has reacted by the time the foam is removed from the mold. There's no need. The blocked isocyanate used in the present invention dissociates into an active isocyanate and a blocking agent during heat treatment, and the active isocyanate further reacts with the linear urethane polymer to form a skin having new and good physical properties. The present invention will be explained below with reference to the drawings.

The figure shows 1 of the method for producing a flexible foam with a skin of the present invention.
This is a manufacturing process diagram of an example, showing a process consisting of the preparation of the skin paint, the preparation of the core material, the molding line, and the post-treatment of the molded product. In this embodiment, the molding line shows a case where the core material is injected into a closed mold, but it is also possible to perform a closed mold injection, in which case the mold closing and injection are reversed. Further, the order of heat treatment and finishing in the post-treatment of the molded product may be reversed. Preparation of paint for skin: A weight average molecular weight of 10,000 to 1 synthesized from a bifunctional polyol, preferably a polyester polyol, a bifunctional isocyanate, preferably a non-yellowing isocyanate, etc.
A one-component urethane lacquer (urethane lacquer) in which 00,000 linear urethane polymer is dissolved in a solvent consisting of a soft solvate is added with a difunctional to polyfunctional blocked isocyanate (per 10 parts by weight of the linear urethane polymer).
Blockysocyanate) For example, the formula: C2QC(CH2
NHCOOC 6 days 4 CH 3 NHCOOC 6 days 5) Compound 3 without 1 and 25 weight.

Prepare a paint for the epidermis. In addition, this paint contains
Of course, colorants and other additives may be added in the same way as with ordinary paints. Core material formulation: The composition of conventional foamed plastics can be used as is.

For example, additives (eg, catalysts, crosslinking agents, chain extenders, blowing agents, etc.) are added to polyether polyols or polyester polyols and isocyanates (eg, diisocyanates) using conventional mixing ratios and mixing methods. Molding line: Paint for the skin is applied to a foam mold such as a resin mold or a metal mold to a film thickness of about 50 mm (application process) and the paint film is dried (drying process).

This drying step may be omitted depending on the case. After drying, the foam mold is closed (mold closing step) and a foamable composition as a core material is injected into the foam mold (injection step). After the core material is foamed and cured after injection (curing process), the foaming mold is opened (mold opening process) and the molded product having a dry skin layer is taken out from the foaming mold (
extraction process). After the molded product has been taken out, a mold release agent is applied to the foam mold (mold post-treatment step) and the mold is returned to the paint application step.
Post-treatment of molded products: The molded products taken out are heated to a predetermined temperature, preferably 145 to 16
000 for a predetermined time, preferably 30 to 90 minutes (heat treatment step) to react the blocked isocyanate to form a cured film, and then finish (finishing step)
・Obtain a flexible foam.

Each foam molded article was molded using samples 0 and m of the skin paint of the present invention, which are obtained by adding a blocked isocyanate to a linear urethane polymer solution shown in Table 2 below, and sample 1, which is made of a linear urethane polymer solution. Table 3 shows the chemical resistance test results for each sample, and Table 4 shows the physical property test results for only the epidermis of each sample.

Table 2 (Units are parts by weight) Note 1 Weight average molecular weight approximately 50,000, 30% solubility Note 2
C2 day 5C (CH2NH
COOC6 days 4CH3NHCOOC6 French) 3 Note 3 Ultraviolet absorber/antioxidant = 50/50 Table 3 Note 1 Epidermal thickness 5
This is a sample with a core material thickness of approximately 5 mm.

Note 2 5 represents the degree to which no abnormality is observed. 4 indicates that the abnormality is slightly observed but not noticeable*.

3 indicates that the abnormality is slight but clearly recognized.

2 indicates that the abnormality is somewhat noticeable.

1 indicates that the abnormality is quite severe.

Note 3 The test method is described below.

(Test method) Attach the molded body to a Gakushin friction tester with the skin facing up.
Next, a white wire cloth impregnated with a prescribed chemical (hair styling product or gasoline) was fixed on the friction element, and the friction element was rubbed back and forth 50 times with a trowel with a load of 500, and the degree of discoloration was determined based on the contamination of the white wire cloth. Check the degree of wear.

Table 4 Note 1 Retention rate = (Characteristic value after test) / (Characteristic value before test) x 100 Note 2 Light resistance test
It rained in the evening, and the black panel temperature was 83±3℃, 4
The test was conducted under the conditions of 00 hours.

Note 3: The heat resistance test was conducted in a drying oven at a temperature of 12,000 for 400 hours. As shown in Table 3, it can be seen that the chemical resistance of Samples R and M of the present invention to which blocked isocyanate was added is much better than that of Sample 1 of the comparative example.

In addition, Table 4 shows that the physical properties of the sample date and m of the present invention are better than those of Sample 1 of the comparative example. It is thought that the

Note that the linear urethane polymer used in the present invention contains 1OH
It is presumed that the active isocyanate generated reacts with the urethane bond in the primary mirror to form an allophanate bond, since it seems that there is no group that easily reacts with isocyanate, such as a group or a monoNH2 group.

As described above, it can be seen that the skinned flexible foam of the present invention is improved in the following points regarding the balance of physical properties of the skin compared to conventional skinned foams.

It was possible to impart chemical resistance without substantially deteriorating the physical properties of the skin obtained from conventional one-component urethane lacquers, and to increase the retention of physical properties after light and heat resistance tests.

Next, the present invention also improves productivity. That is, since the blocked isocyanate used in the present invention is inactive at room temperature, the storage stability of the skin paint is good, and since it does not react at room temperature, alcohol-based soft solvents can also be used as the solvent. As a result, neither the working environment nor the sprayability of the paint deteriorates. Linear urethane polymer itself forms a skin with good physical properties, so
After the core material is foamed and cured, the molded product can be easily removed from the foaming mold even if the blocked isocyanate in the skin remains unreacted, so when a certain amount of molded product has accumulated, for example, a lot of 3 solids at a time can be removed. Advantages such as the fact that the molding cycle time is not affected even if post-processing takes a long time can be obtained.

[Brief explanation of drawings]

The figure is a manufacturing process diagram showing an example of the manufacturing method of the present invention.

Claims (1)

[Scope of Claims] 1. A flexible foam with a skin, characterized in that a skin made of a crosslinking reaction product of a linear urethane polymer and a blocked isocyanate is formed on the surface of a polyurethane foam. 2. A skin coating consisting of a linear urethane polymer and a blocking isocyanate is applied to a foaming mold, and a foamable resin composition for a core material is injected into the foaming mold and foamed, and then the obtained molded product is heat-treated to form the linear A method for producing a flexible foam for skin, characterized by reacting a urethane polymer with a blocked isocyanate.