JP2011213928A - Heat-resistant coating agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat resistant coating agent having no problem in which many of marketed heat resistant coating agents are made of polysiloxane based ones and are applied onto a metal and the like to increase heat insulation, however the conventional heat resistant coating agent has poor adhesiveness to a rubber and plastics because of its polysiloxane based one and actually hardly can be used.SOLUTION: The heat resistant coating agent is formed by mixing 25 to 50 pts.wt. the following component B to 100 pts.wt. the following component A. A: siloxane prepolymer in a liquid shape, B: an isocyanate compound containing as a principal component a crude MDI having 10 to 20 wt.% isocyanate content.

Description

  The present invention relates to a heat resistant coating agent.

  Rubber and plastic are used in various applications due to their elasticity and low cost. However, rubber and plastic are inherently vulnerable to heat and cannot be used in a high temperature region.

  For example, even if it is thought that an elastic pavement is constructed by mixing crushed pieces of rubber as aggregate on asphalt pavement, when asphalt emulsion is laid, it is heated to about 170 to 180 ° C, The rubber cannot be used because it causes phenomena such as melting and adhesion at temperature.

  For this reason, elastic pavements must be expensive resin pavements at present. Therefore, the elastic pavement itself is reduced. Elastic pavement is essential for noise reduction and for bridge piers and highways.

  Conventionally, what is called a heat resistant coating is commercially available. This is often polysiloxane-based. This is for applying to metal etc. and improving heat retention.

  However, conventional heat-resistant coating agents have poor adhesion to rubbers and plastics, which are polysiloxanes, and can hardly be used in practice. The inventor also applied this to a rubber piece, mixed it into an asphalt emulsion, and stirred it, so that it often peeled off and could not be used as an elastic aggregate for asphalt.

  Then, this inventor provides the heat resistant coating agent which does not have the above faults.

In view of the above situation, the present inventor has completed the heat resistant coating agent of the present invention as a result of intensive studies, and the feature thereof is that the following component B is 25 to 25 parts by weight based on 100 parts by weight of the following component A. 50 parts by weight mixed heat-resistant coating agent,
A: Siloxane prepolymer in liquid form,
B: An isocyanate compound mainly composed of crude MDI having an isocyanate content of 10 to 20% by weight.

Here, component A is a siloxane prepolymer. Siloxane prepolymers are those that cure with moisture in the air. When used alone, the curing reaction is slow. Therefore, many catalysts are mixed to accelerate curing when used. The catalyst may be mixed from the beginning. If it does so, hardening will be started if it touches moisture.
In the present invention, alkylphenylsiloxane is preferred. This is because of excellent heat resistance.

  The molecular weight of the siloxane prepolymer is not particularly limited, but is preferably about 500 to 100,000. This is from handling and pot life.

  In order to further improve the heat resistance, the component A may be mixed with a powder of a metal oxide such as titanium oxide, aluminum oxide, or silicon dioxide. The mixing amount is 20 to 50 parts by weight with respect to 100 parts by weight of the prepolymer.

  Further, when the viscosity of component A is high, the viscosity may be adjusted so that it is convenient for handling. That is, an organic solvent may be mixed. For example, xylene, ethylbenzene and the like. The mixing amount may be determined by the viscosity.

  As this component A, a siloxane-based commercially available heat-resistant coating agent can be used.

Component B is a one-component curable isocyanate compound. That is, it is cured by moisture in the air.
Crude MDI is polymethylene polyphenyl polyisocyanate. Furthermore, the isocyanate content is 10 to 20% by weight, preferably 14 to 18% by weight. Among the isocyanates, crude MDI is good, and the others have problems in adhesion and heat resistance.

  The point of the present invention is that isocyanate is mixed with a conventional siloxane-based heat-resistant coating agent. It is novel to mix a resin-based material with such a siloxane-based material, which is not usually conceived.

  In Component B, the above-mentioned crude MDI is the main component (90% by weight or more), but there is no problem even if an additive that is usually mixed is added.

  The mixing ratio of Component A and Component B is preferably 25 to 50 parts by weight of Component B with respect to 100 parts by weight of Component A.

  The manufacturing method of this invention coating agent should just mix the component A and the component B with liquids. Since the curing starts from the time of mixing, it is necessary to apply to the object to be coated within a certain time. This time (pot life) depends on the curing time of siloxane, the curing time of isocyanate, etc., and is usually 20 to 50 minutes.

  As an application of the present invention, there is a coating applied to an elastic aggregate mixed with the asphalt emulsion described above. This is for imparting heat resistance to heat-sensitive materials such as rubber and plastic. Specifically, the asphalt emulsion is usually heated to about 170 to 180 ° C. It is softened by heating, mixed with aggregates, etc., and laid on the road. Therefore, it cannot be used if it melts at 170-180 ° C. or loses its weight.

Normally, rubber and plastic cannot withstand this temperature, and thus cannot be used, but those coated with the coating agent of the present invention can withstand this temperature sufficiently.
In such a method for producing an elastic aggregate, a mixture of component A and component B need only be sprayed onto the aggregate piece. For example, the aggregate is rolled on a net and sprayed from above and below.

  Furthermore, a material in which inorganic powder is fixed to an aggregate of rubber or plastic with an adhesive has been used recently. When the coating agent of the present invention is used for this adhesive, heat resistance is imparted in addition to the function as an adhesive. Therefore, the aggregate on which the inorganic powder is fixed can be used as a mixture with asphalt.

In the method of manufacturing the aggregate to which the inorganic powder is fixed, the component A, the component B, the aggregate and the powder are simply put in one container and mixed. Since the inorganic powder is mixed, the aggregate is bonded to each aggregate by a coating agent without bonding the aggregates.
The mixing ratio is 50 to 1000 parts by weight (preferably 200 to 600) for the aggregate such as rubber and 100 to 300 parts by weight (preferably for the inorganic powder) with respect to 100 parts by weight of the coating agent. 150-200).

The coating agent of the present invention can be applied to any asphalt aggregate as described above. Basically, it is applied to plastic or rubber having no heat resistance to impart heat resistance, but may be applied to, for example, metal, wood, or any other material.
Although the application | coating thickness of this invention coating agent is free, 0.05-0.5 mm is good and it is 0.1-0.3 mm more suitably. This is sufficiently effective.

The present invention has the following great effects.
(1) The heat resistance of an object to be coated is improved simply by coating.
(2) It can also be used for purposes other than improving the heat resistance of an object to be coated. For example, heat retention and other improvements.
(3) Good adhesion and adhesion to rubber and plastic.
(4) It can also be used as a heat-resistant adhesive.

  Hereinafter, it demonstrates in detail along an Example.

Example 1
As Component A, commercially available “Thermo Resin-400P (trademark)” of Chugai Shoko Co., Ltd. was used. This contains 5 to 35% by weight of polyalkylphenylsiloxane, titanium oxide, xylene and ethylbenzene, respectively.

  Component B was crude MDI with an isocyanate pigment content of 15% by weight and a viscosity of 2000 mPa · s.

Component A and Component B were mixed at a normal weight ratio of 70:30 and stirred. This was applied to a urethane resin sheet (5 cm × 5 cm × 5 mm). The coating thickness was 0.2 mm.
Moreover, the same resin sheet which does not apply | coat anything was prepared as a comparative example.

The two were heated and the pyrolysis temperature was examined. Both decomposed at 286 ° C. Therefore, the temperature at which the rubber undergoes thermal decomposition did not change.
Next, it heated gradually, measuring the weight loss. The temperature was raised from 30 ° C. to 350 ° C. at 10 ° C./min. The temperature at which the weight decreased by 1% was examined and was as follows.
Example: 219 ° C
Comparative example: 161 ° C

  From this result, it was found that the weight was gradually reduced when maintained at 170 ° C. for a long time. Therefore, it was found that this urethane resin cannot withstand an environment of 170 ° C. or higher, but it can sufficiently withstand if the coating agent of the present invention is applied.

Next, a rubber aggregate to be mixed with asphalt was manufactured.
Components A and B were the same as those described above. To 100 parts by weight of this mixture, 15 parts by weight of a large rubber aggregate (about 5 mm), 30 parts by weight of a small rubber aggregate (about 1.2 mm), and 100 parts by weight of cement powder are mixed, Had made.
The aggregate was made with cement powder fixed by resin around it.

  This was mixed with an asphalt emulsion at 180 ° C., but the aggregate was not melted or deformed until the temperature dropped after construction (10 to 30 minutes).

Claims (1)

The heat-resistant coating agent characterized by mixing 25 to 50 parts by weight of the following component B with respect to 100 parts by weight of the following component A,
A: Siloxane prepolymer in liquid form,
B: An isocyanate compound mainly composed of crude MDI having an isocyanate content of 10 to 20% by weight.