JPS5841298B2 - Hashikake Enkabinirjiyushihatsupoutaino Seizouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an extremely simple method that does not soften at high temperatures.
The present invention relates to a method for producing a cross-linked vinyl chloride resin foam that has excellent dimensional stability and solvent resistance.

Conventionally, many methods have been known for producing hard or soft foams of vinyl chloride resin (hereinafter sometimes abbreviated as PvC), but most of these foams are
It has a major drawback of lacking dimensional stability because it softens when exposed to high temperatures of 0° C. or higher or when it comes into contact with a solvent such as tetrahydrofuran, cyclohexanone, or dimethylformamide, causing bubbles to disappear and volume to decrease.

The present inventors have been conducting research on PvC bridging reactions for many years,
Certain triazine compounds (i.e. 2-R-
4,6-dithiol-S-triazine or its metal salt)
We have already applied for a patent for the PvC bridging method using
No. 4), but in the present invention, in response to the foaming reaction that is completed within a relatively short period of time, the compound having excellent cross-linking reactivity with PvC is blended, and the blowing agent gas is added. The cross-linking reaction of PvC occurs during expansion due to release to make the melt properties of the resin, namely melt viscosity, melt elasticity and melt surface tension suitable for foaming, to form a favorable foaming state, and at the same time the cross-linking reaction of PvC occurs. By completing this process, it is possible to produce a cross-linked PVC foam that does not soften at high temperatures, has excellent dimensional stability, and has excellent solvent resistance.

The method of the present invention will be explained in more detail below.

Now, if we look at the change over time in the specific gravity at the foaming temperature of a foam obtained with a normal flexible PVC foam composition, we can see that the foaming reaction is completed in a relatively short time as shown in the reference example in Figure 1, resulting in a foam with the lowest specific gravity. When heating for a longer period of time, the foam disappears due to softening of the PVC, which often results in the volume of the foam being reduced and the specific gravity increasing.

Therefore, by cross-linking PVC, the melting characteristics of the resin at the time of foaming can be adjusted to be suitable for foaming, and the cross-linking reaction is completed when foaming is completed, that is, when the minimum specific gravity is reached. It is considered that if the shading agent is selected, the foaming and crosslinking reactions can be completed almost simultaneously, and the specific gravity of the foam can be maintained at the minimum S state.

Now, the crosslinking reaction rate of the crosslinking agent used in the present invention for soft PvC having a composition similar to that shown in Figure 1 varies depending on the composition, as shown in Figure 2, but is generally fast enough to correspond to the decomposition rate of the blowing agent, that is, the foaming rate. As a result, the foam can be obtained with a minimum specific gravity of g.

Such a high crosslinking reactivity is completely absent from the range of conventionally known crosslinking agents for PVC, and the present invention, which applies this series of crosslinking agents to the composition of PVC foam, is extremely original. It can be said that it is a thing.

Therefore, by appropriately combining blowing agents having a decomposition (foaming) rate corresponding to the crosslinking rate, it is possible to produce crosslinked foams having various specific gravities as shown in the Examples.

The triazine compound which is an important crosslinking agent in the present invention is 2-R-4.6dithiol-S represented by the following formula.
-) IJ azine or its metal salt.

In the above formula, R is, for example, OR1, SR1, N
Examples include H2, NHR2, NR3R4, phenyl, naphthyl, morpholino, hydrazino, etc., R1 is hydrogen or a hydrocarbon residue, and a preferable example of R1 is CnH2
n+1 (n=1 to 8), phenyl, and preferable examples of R2, R3, and R4 include phenyl, CnH2
n+1 (m=1 to 18), and R3 and R4
may be connected at the other end to form a ring.

The crosslinking property of the crosslinking agent is determined by R in the compound represented above.
- basic groups such as -NHR2, -N
R3R4 is superior.

Representative examples of such dithiol-8-)riazine derivatives include 2-dimethylamino, 2-dibutylamino-
2-octylamino, 2-cyclohexylamino, 2-
Benzylamino, 2-dibenzylamino, 2-phenylamino, 2-phenylbenzylamino, 2-methylphenylamino, 2-anilino, 2-diphenylamino, 2-
Mention may be made of α-naphthylamino, 2-β-naphthylamino, 2-benzylthio, 2-ethoxy and 2-phenoxy-4,6-dithiol-S-triazine.

In addition, as the metal salt of 2-R-4.6-sithio-S-) riazine, alkali metals such as Li, Na, K, etc. of the compound, alkaline earths such as Ca, Mg, Ba, Cd, Zn, Sr, etc. Examples include salts of metals, Al, Sn, Pb, Ni, etc., and salts of organic metals such as dibutyltin and tributyltin salts of the compounds.

Among these metal salts, alkali metal salts and alkaline earth metal salts are preferable as crosslinking agents from the viewpoint of crosslinking reaction rate corresponding to the decomposition rate of the blowing agent and cost.

For example, the reaction rate increases in the order of 2-R-4.6-dithiol-S-4 lyazine (I) < alkaline earth metal salt of (I) << alkali metal salt of (I).

Furthermore, the crosslinking agent used in the present invention is 2-dibutylamino 4,6-sithiorus, which is highly compatible with PVC, has high crosslinking reactivity, and is certified as an existing substance.
-Triazines are most preferred.

This compound exhibits crosslinking reactivity when added to the PvC foaming composition as such or as an alkaline earth or alkali metal salt, if necessary in the presence of an acid acceptor such as magnesium oxide or calcium oxide.

The amount of these crosslinking agents added is usually 1 to 10 parts by weight per part by weight of PVC IOO.

These crosslinking agents can be added to the PvC foaming composition by adding them directly in the form of a fine powder or in the form of a paste or solution to a plasticizer or methyl selon.

Since the crosslinking reaction normally proceeds at a temperature of 100° C. or higher, the present invention can be carried out under conventional foam molding processing conditions.

In the present invention, a crosslinking aid may be present in order to promote the crosslinking reaction between the crosslinking agent and polyvinyl chloride.

Examples of cross-linking aids include polyoxyethylene alkyl ethers such as polyethylene glycol and polyoxyethylene lauryl ether, polyoxyethylene compounds such as 2-ethylhexylic acid di- or monoester of polyethylene glycol, aliphatic compounds such as tributylamine, diphenylamine, etc. Aromatic amines, alkanolamines such as dimethyloctylamine, triethanolamine, tri(diethylene glycol)amine, tri(polyethylene glycol)amine, and guanidine compounds such as diphenylguanidine, MgO, CaO, ZnO, SrO, P
bO1Mg(OH)2, MgCO3, CaCO3,
Either a basic metal compound such as BaCO3, barium stearate or calcium stearate, or a polyhydric alcohol such as trimethylolpropane or glycerin is used.

Among these crosslinking aids, basic compounds also act as acid acceptors, and therefore, their use in combination with crosslinking agents is recommended.

The amount of the crosslinking aid used is usually 0 to 100% by weight based on the crosslinking agent.

Next, as the blowing agent, all conventionally known inorganic and organic blowing agents and volatile solvents can be used, but as shown in the examples, 1 to 20 parts of hydrogen carbonate can be used depending on the processing temperature and the type of crosslinking agent. ) One or more combinations of IJum, paratoluenesulfonyl hydrazide, 4,41oxybisbenzenesulfonylhydrazide or azodicarboxylic acid amide are effective.

In addition to vinyl chloride homopolymers, vinyl chloride resins include vinyl esters such as vinyl acetate, vinyl ethers, esters of acrylic acid or methacrylic acid, maleic acid, fumaric acid, acrylonitrile, vinylidene chloride, copolymers with ethylene, propylene, etc., and ethylene. -It also includes graft copolymers obtained by graft polymerizing vinyl chloride onto vinyl acetate copolymers.

Furthermore, mixtures of these copolymers and vinyl chloride homopolymers and mixtures of polyvinyl chloride and other thermoplastic resins can also be used.

In the method of the present invention, additives such as plasticizers, stabilizers, foam accelerators, processing aids, impact improvers, fillers, pigments, acid acceptors, gelling agents, etc. Can be added.

In addition, in the method of the present invention, the foam can be produced using known methods such as calendering, extrusion, paste processing,
It is shaped using a vacuum forming method or the like, and an appropriate mold.

Further, in the method of the present invention, the bridging and foaming can be carried out in one stage, but it is also possible to advance the bridging slightly in advance and then raise the temperature further to complete the bridging and bridging.

※※ The present invention will be specifically explained below using examples.

A semi-gelled sheet made by heating the PvC paste foamable composition shown in the reference example column in the reference example table at 120°C for 5 minutes was further heated to 190°C and foamed (normal pressure one-stage foaming method). Figure 1 shows the change in specific gravity of the foam.

The resulting foam was completely dissolved in tetrahydrofuran,
It is also clear that the specific gravity is difficult to maintain at a constant level during heating, resulting in a lack of dimensional stability such as a decrease in volume.

Example 1.2.3 When a semi-gelled sheet made by heating the PvC paste foamable composition shown in the table at 120°C is further heated to 1190°C for 6 minutes, the specific gravity becomes 0.50, 0.41.0. 34
A colorless foam is obtained.

All PvC used was 100% in tetrahydrofuran.
The foam is insoluble (Fig. 2), and its morphology does not change even when sprayed with tetrahydrofuran;
Even when heated to 90°C for more than 6 minutes, the specific gravity (
There is almost no change in volume), and it has excellent dimensional stability.

Example 4.5 The paste formulation shown in the table (Example 4) was heated at 190°C for 15 minutes.
The roll-kneaded mixture (Example 5) was heated at 190°C for 10 minutes each.
Colorless foams with a specific gravity of 0.43 can be obtained in both cases by heating for 1 minute.

This specific gravity does not change even when heated for a longer period of time, and volume stability is observed.

The PvC used was 83.6 for tetrahydrofuran, respectively.
．． It is 89.8% insoluble.

Example 6 The formulation shown in the table is an example using azodicarboxylic acid amide as a blowing agent, and a foam with a specific gravity of 0.33 can be obtained by heating at 200° C. for 6 minutes.

50% of the PvC used is insoluble in tetrahydrofuran.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the change in specific gravity of the foam due to heating, and FIG. 2 is a diagram showing the solvent resistance of the vinyl chloride resin foam obtained in response to the molding time of the foam.

Claims (1)

[Claims] 1 Vinyl chloride resin, a triazine compound or a triazine compound, and an auxiliary agent and a blowing agent selected from a polyoxyethylene compound, an aliphatic amine, an aromatic amine, an alkanolamine, a guanidine compound, a basic metal compound, and a polyhydric alcohol. 1. A method for producing a cross-linked vinyl chloride resin foam, which comprises blending and heating and foaming the foam.