JPS6153371B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to polyurethane compositions. Urethane prepolymers having isocyanate groups at the molecular ends are used in applications such as elastomers, waterproofing materials, sealing materials, and coating materials due to their ease of handling, which is a one-component reaction type. However, this urethane prepolymer has a very slow curing reaction and, as a result, has no formability, so its use has been mainly limited to thin layers such as coating materials. As a method to improve this drawback, curing using water has been proposed, but this method is difficult due to the compatibility of water and urethane prepolymers, especially diene chain-containing prepolymers, which have no compatibility with water. Not applicable. Further, even if the temperature or the amount added is changed, there is a limit to the adjustment of the curing rate, and sufficient effects cannot be expected. In order to eliminate these drawbacks, the present inventors investigated the effects of adding various additives, and found that the vulcanization accelerator for solid rubber contributed to the curing of the urethane prepolymer, and that the It was found that it is related only to the terminal isocyanate group, regardless of the double bond. The present invention has been made based on such knowledge, and aims to provide a polyurethane composition that can arbitrarily control the curing speed of the urethane prepolymer and can be applied to various uses with good formability. It is. The present invention is a sheet-formable polyurethane obtained by blending sodium dibutyldithiocarbamate or zinc butylxanthate as a vulcanization accelerator into a urethane prepolymer containing isocyanate groups at the molecular terminal, which is a reaction product of an organic polyisocyanate and a liquid rubber. It is a composition. The isocyanate group-containing prepolymer used in the present invention is a reaction product of an organic polyisocyanate and a liquid rubber. Examples of the organic polyisocyanate include tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, polymethylene polyphenyl polyisocyanate, liquid modified diphenylmethane diisocyanate, xylylene diisocyanate, cyclohexanephenylene diisocyanate, cyclohexyl diisocyanate, and chlorophyllodisocyanate. Enylene diisocyanate, naphthalene
1,5-diisocyanate, xylylene-2.
2'-diisocyanate, isopropylbenzene-
Examples include an addition reaction product of 2,4-diisocyanate, polypropylene glycol or triol and tolylene diisocyanate, and an addition reaction product of 1 mol of trimethylolpropane and 3 mol of tolylene diisocyanate. Next, in the present invention, a liquid rubber having an active hydrogen group such as a hydroxyl group, an amino group, an imino group, a carboxyl group, or a mercapto group at the molecular end is used. These liquid rubbers have a number average molecular weight of 500
~25,000 diene polymers and copolymers with 4 to 12 carbon atoms, as well as these diene monomers and 2 to 22 carbon atoms.
There are copolymers with α-olefinic addition polymerizable monomers. Specific examples include polybutadiene homopolymer, polyisoprene homopolymer, butadiene-isoprene copolymer, butadiene-styrene copolymer, butadiene-acrylonitrile copolymer, butadiene-2-ethylhexyl acrylate copolymer, butadiene-n-octadecyl acrylate copolymer, and the like. Among them, the viscosity is 2000 poise or less, more preferably 500 poise or less.
It is preferable to use a polymer having a chemical structure of 50% or more of 1,4 bonds and a poise or less. The urethane prepolymer containing molecular terminal isocyanate groups used in the present invention is usually composed of the above organic polyisocyanate and liquid rubber in an NCO/OH (equivalent ratio).
It is obtained by reacting at a reaction temperature of 30 to 150°C for 10 minutes to 10 hours under conditions of 1.5 or higher, under an inert gas flow such as dry nitrogen. In addition, the terminal isocyanate group content in the urethane prepolymer is 1 to 1.
20% by weight, preferably 2 to 15% by weight. The main component of the composition of the present invention is basically the above-mentioned urethane prepolymer containing an isocyanate group at the end of the molecule, but in order to improve the stability during storage,
It may be a blocked urethane prepolymer in which a blocking agent for masking the isocyanate groups is bonded to the terminal isocyanate groups of the polyisocyanate. Here, blocking agents include phenols such as phenol, cresol, xylenol, and nonylphenol; alcohols such as methanol, ethanol, and isopropanol; lactams such as caprolactam and butyrolactam;
Examples include oximes such as acetoxime, methyl ethyl ketoxime, and cyclohexanoxime, other imides, and esters. In any case, this blocked polyisocyanate is usually
By heating at 100°C or higher, the blocking agent dissociates and free isocyanate is regenerated, resulting in polyisocyanate. Next, in the present invention, sodium dibutyldithiocarbamate or zinc butylxanthate is used as a vulcanization accelerator. In addition, sodium hydroxide, calcium oxide, magnesia, zinc white, etc. can also be used as a vulcanization accelerating aid if necessary. The blending ratio of the urethane prepolymer and vulcanization accelerator is determined in consideration of the type of urethane prepolymer, the operating temperature, etc., so as to obtain a desired curing time. Usually, it is blended in a proportion of 0.05 to 10% by weight, preferably 0.1 to 5% by weight, based on the urethane prepolymer. In addition to the above two components, auxiliary components such as plasticizers, fillers, reinforcing agents, and stabilizers may be appropriately added to the polyurethane composition of the present invention as required. The polyurethane composition of the present invention is obtained by sufficiently kneading the above-mentioned components, and the temperature at that time is not particularly limited. Types of urethane prepolymers,
Determined by viscosity, curing time, usage, etc. The temperature is usually selected from room temperature to 250°C, preferably from room temperature to 200°C. The polyurethane composition of the present invention is a one-component reaction type, and can be used not only as an adhesive or a sealant that does not come into contact with the atmosphere, but also suitable for producing thick molded products. Further, the curing speed can be arbitrarily adjusted by adjusting the amount of the vulcanization accelerator added. Furthermore, it is possible to obtain a material having physical properties equivalent to or better than those obtained by moisture curing. Furthermore, since rapid gelation does not occur, continuous molding into sheets and the like is possible, and shapeability and moldability are also good. In addition, one of the features of the present invention is that it has excellent handling and workability. Therefore, the polyurethane composition of the present invention can be used as an adhesive, a sealant,
It can be advantageously used as various coating agents and in the production of molded products such as waterproof sheets. Next, the present invention will be explained in detail with reference to Examples. Examples 1 to 3, Comparative Examples 1 to 3, and Reference Examples 1 to 4 The time required for the mixtures having the formulations shown in Table 1 to gel at 150°C was measured. Similarly, it was press-molded at 150°C for 30 minutes and then cured at room temperature for one week to produce a 2 mm thick sheet and its physical properties were measured. The results are shown in Table 1. 【table】

Claims (1)

[Claims] 1. A sheet-formable polyurethane composition comprising a urethane prepolymer containing molecular terminal isocyanate groups, which is a reaction product of an organic polyisocyanate and a liquid rubber, and sodium dibutyldithiocarbamate or zinc butylxanthate as a vulcanization accelerator.