Polyisocyanate and process for producing the same

Details Polyisocyanate and process for producing the same Polyisocyanate and process for producing the same

2000-08-30

2002-10-22

Seidleck, James J. (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From reactant having at least one -n=c=x group as well as...

C528S067000, C528S085000

Reexamination Certificate

active

06469122

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a novel polyisocyanate. More particularly, the present invention is concerned with a novel polyisocyanate which is obtained by reacting at least one diisocyanate selected from the group consisting of an aliphatic diisocyanate and an alicyclic diisocyanate with a polyol having a number average molecular weight of from 3,000 to 30,000 and an average number of hydroxyl groups of from 2 to 3 and which contains allophanate linkages and urethane linkages in a specific ratio. The polyisocyanate of the present invention exhibits a high curing rate and a low viscosity. Further, the polyisocyanate, upon being cured, not only has no surface tack and exhibits a low modulus-in-tension property, but also exhibits a high tensile elongation property without a need for a plasticizer. Therefore, the polyisocyanate of the present invention can be advantageously used as a sealant. The present invention is also concerned with a sealant comprising the polyisocyanate. Moreover, the present invention is concerned with a method for effectively and efficiently producing the polyisocyanate which, upon being cured, is improved with respect to a low modulus-in-tension property and a high tensile elongation property.
2. Prior Art
A polyisocyanate is advantageous in that a cured resin obtained by curing a polyisocyanate, by utilizing the high reactivity of isocyanate groups contained therein, exhibits excellent mechanical properties, such as excellent flexibility and chemical resistance, so that a polyisocyanate is widely used for a coating material, an adhesive, a sealant, a waterproof material, a foam, an elastomer and the like. A polyisocyanate can be produced using a diisocyanate as a main raw material. Polyisocyanate-based curable resin compositions are classified into those of one-pack and two-pack types. A one-pack type curable resin composition containing a polyisocyanate is cured by moisture in the air or the like. On the other hand, in the case of a two-pack type curable resin composition containing a polyisocyanate, the polyisocyanate is mixed, just prior to use, with a polyol to cause a reaction of the isocyanate groups in the polyisocyanate with the hydroxyl groups in the polyol, thereby curing the composition.
Of polyisocyanates, a polyisocyanate produced using an aliphatic diisocyanate or an alicyclic diisocyanate as a main raw material has an advantage in that a cured resin obtained by curing the polyisocyanate has excellent weatherability. Therefore, there have hitherto been many proposals with respect to a polyisocyanate produced using an aliphatic diisocyanate or an alicyclic diisocyanate as a main raw material.
Also known is a polyisocyanate having a carbodiimide, a uretdione, an oxadiazinetrione, a biuret, a urethane, an allophanate or an isocyanurate skeleton.
Biuret polyisocyanates are disclosed in Unexamined Japanese Patent Application Laid-Open Specification No. 49-134629 (corresponding to U.S. Pat. No. 3,976,622), Examined Japanese Patent Application Publication No. 61-26778 (corresponding to U.S. Pat. No. 4,176,132), Examined Japanese Patent Application Publication No. 62-41496 (corresponding to U.S. Pat. No. 4,290,969), Unexamined Japanese Patent Application Laid-Open Specification No. 63-174961 (corresponding to U.S. Pat. No. 4,837,359), Examined Japanese Patent Application Publication No. 2-62545 (corresponding to U.S. Pat. No. 4,983,762), Examined Japanese Patent Application Publication No. 5-17222, Unexamined Japanese Patent Application Laid-Open Specification No. 8-225511 (corresponding to U.S. Pat. No. 5,641,851), and the like.
Isocyanurate polyisocyanates are disclosed in Unexamined Japanese Patent Application Laid-Open Specification No. 55-38380 (corresponding to U.S. Pat. No. 4,324,879), Unexamined Japanese Patent Application Laid-Open Specification No. 57-150677 (corresponding to U.S. Pat. No. 4,412,073), Unexamined Japanese Patent Application Laid-Open Specification No. 57-47319, Unexamined Japanese Patent Application Laid-Open Specification No. 63-57577, and the like.
Allophanate polyisocyanates are disclosed in British Patent No. 994890, Unexamined Japanese Patent Application Laid-Open Specification No. 7-304724, and the like.
Conventionally, urethane polyisocyantes have been widely used as a sealant for use in the architecture field in order to provide watertightness and airtightness. Especially, an elastic sealant using a urethane sealant has excellent physical properties, so that there has been a great increase in commercial demand for the elastic sealants.
With respect to urethane polyisocyanates for sealants used in the architecture field, reference can be made, for example, to Unexamined Japanese Patent Application Laid-Open Specification No. 3-111448, which discloses a high molecular weight urethane polyisocyanate having terminal isocyanate groups, which is obtained by reacting two different types of polypropylene glycols respectively having average molecular weights of 3,000 and 5,000 with 4,4′-diphenylmethane diisocyanate (hereinafter, frequently referred to as “MDI”).
Unexamined Japanese Patent Application Laid-Open Specification No. 4-370146 discloses a high molecular weight urethane polyisocyanate having terminal isocyanate groups, which is obtained by reacting with MDI a polypropylene glycol having an average molecular weight of 3,000 and a polypropylene ether triol having an average molecular weight of 300.
Unexamined Japanese Patent Application Laid-Open Specification No. 6-080755 discloses a high molecular weight urethane polyisocyanate having terminal isocyanate groups, which is obtained by reacting with xylylene diisocyanate a polypropylene glycol having an average molecular weight of 3,000 and a polypropylene ether triol having an average molecular weight of 3,000.
Unexamined Japanese Patent Application Laid-Open Specification No. 6-256499 discloses a high molecular weight urethane polyisocyanate having terminal isocyanate groups, which is obtained by reacting with MDI a polyalkylene ether triol having an average molecular weight of 7,000 and a polyalkylene ether triol having an average molecular weight of 5,000.
Unexamined Japanese Patent Application Laid-Open Specification No. 3-215554 discloses a high molecular weight urethane polyisocyanate having terminal isocyanate groups, which is obtained by reacting with MDI a polyalkylene ether triol having an average molecular weight of 3,000.
Unexamined Japanese Patent Application Laid-Open Specification No. 5-209165 discloses a high molecular weight urethane polyisocyanate having terminal isocyanate groups, which is obtained by reacting with tolylene diisocyanate a polypropylene ether diol having an average molecular weight of 4,000 and a polypropylene ether triol having an average molecular weight of 10,000.
Examined Japanese Patent Application Publication No. 51-28680 discloses a reaction product of a high molecular weight polyisocyanate obtained from a polyhydroxyl compound having a molecular weight of from 500 to 10,000 and a polyisocyanate precursor with a monovalent polyether alcohol.
A urethane sealant for use in the architecture field is required to have a high curability by moisture and a low viscosity. It is further required that the urethane sealant should, upon being cured, not only have no surface tack, but also exhibit an excellent stain resistance, a low modulus-in-tension property and a high tensile elongation property. However, a sealant which is improved with respect to all of the above-mentioned properties has not been obtained from the conventional urethane polyisocyanate mentioned above.
In any conventional method for producing the urethane polyisocyanate mentioned above, the reaction of a polyol with a diisocyanate is performed in an hydroxyl group/diisocyanate group equivalent ratio of approximately 1/1. The polyisocyanate produced under such reaction conditions has a high molecular weight due to the formation of urethane linkages.
Generally, the use of a high molecular weight resin as a

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