Solid, self-bondable organic polymers and methods for using same

Abstract

Solid compositions made from or coated with a non-melting organic polymer having a main glass transition temperature of at least 65 C., few if any isocyanate groups and a wet aged glass transition temperature of up to 60 C. are self-bonding materials that are useful in a variety of adhesive and molding operations. Under conditions of heat and moisture, these compositions will self-bond. The compositions can be used as adhesive coatings, which are solid and non-tacky and thus can be transported and stored easily under ambient conditions. These compositions are especially useful in applications in which, due to the location and/or orientation of the substrates, liquid or melting materials cannot be applied easily or will run off the substrates.

Claims

1. A method for forming a bonded mass of adhered solid pieces, comprising: a) forming a mass of two or more separate solid pieces, such that a contacting surface of each of said solid pieces is in contact with a contacting surface of one or more adjacent solid pieces at one or more bondlines, wherein said contacting surfaces each are of a solid, non-melting organic polymer having a main dry glass transition temperature as measured by dynamic mechanical thermal analysis of 40 to 130 C., a density of at least 500 kg/m.sup.3, no more than 0.25% by weight isocyanate groups and a wet aged glass transition temperature, as measured by dynamic mechanical thermal analysis, at least 15 C. lower than the main dry glass transition temperature but no greater than 60 C.; and b) heating the mass to a temperature between 20 C. to 100 C. in the presence of water or steam and an applied pressure between 5 MPa to 20 MPa to bond the solid pieces at the bondline or bondlines to form the bonded mass.

2. The method of claim 1 wherein in step a) said two or more separate solid pieces are coated substrate pieces formed by forming a coating the solid, non-melting organic polymer onto multiple substrate pieces.

3. The method of claim 1, wherein the solid, non-melting organic polymer contains urethane groups.

4. The method of claim 3, wherein the solid, non-melting organic polymer has a main glass transition temperature of 65 to 110 C.

5. A method for forming a bonded mass of adhered solid pieces, comprising: a) forming a mass of two or more separate solid pieces, such that a contacting surface of each of said solid pieces is in contact with a contacting surface of one or more adjacent solid pieces at one or more bondlines, wherein said contacting surfaces each are of a solid, non-melting organic polymer produced in a reaction of a reaction mixture containing at least one liquid polyol and at least one liquid polyisocyanate compound in which the isocyanate index is 0.3 to 0.9, the organic polymer having a main glass transition temperature as measured by dynamic mechanical thermal analysis of 40 to 130 C., a density of at least 500 kg/m.sup.3 and no more than 0.25% by weight isocyanate groups; and b) heating the mass to a temperature between 20 C. to 100 C. in the presence of water or steam and an applied pressure between 5 MPa to 20 MPa to bond the solid pieces at the bondline or bondlines to form the bonded mass.

6. The method of claim 5 wherein in step a) the two or more separate pieces are prepared by applying the reactive mixture to the surface of multiple substrate pieces, and curing the reactive mixture to form multiple substrate pieces coated with a solid, non-melting polymer.

7. The method of claim 5, wherein the solid, non-melting organic polymer has a main glass transition temperature of 65 to 110 C. and a wet aged glass transition temperature of no greater than 60 C.

8. The method of claim 5 wherein the polyol is a compound or mixture of compounds having an average functionality of 2.5 to 6 and an average hydroxyl equivalent weight of 50 to 150.

9. The method of claim 5 wherein the polyol is a compound or mixture of compounds having an average functionality of 3 to 4 and an average hydroxyl equivalent weight of 60 to 100.

10. The method of claim 5 wherein the polyisocyanate has an average functionality from 2.2 to 3.5 and an average isocyanate equivalent weight from 80 to 200.

11. The method of claim 5 wherein the polyol is a polyether polyol and the polyisocyanate is a polymeric MDI.

12. The method of claim 5 wherein the isocyanate index is 0.45 to 0.65.

Description

EXAMPLE 1

(1) 25 parts of an 85 equivalent weight, trifunctional glycerine-initiated poly (propylene oxide) polyol, 2.61 parts of a 2.7 functionality, 134 isocyanate equivalent weight polymeric MDI and 0.05 of a tin catalyst are mixed together at room temperature. The isocyanate index is 0.66. 2.510 cm aluminum plates are coated by immersing it in the liquid mixture and then placing the coated plates in an 80 C. oven for 30 minutes to cure the reaction mixture. A solid, non-cellular polyurethane film forms on the surface of the aluminum plates.

(2) Another portion of the reaction mixture is poured onto a plaque mold, cured at 80 C. for 30 minutes, and the glass transition temperature is measured by DMTA. The polymer exhibits a main T.sub.g of 97 C.

(3) Two of the coated aluminum plates are stacked crosswise to form a 2.52.5 cm overlap area. A 2.7 kg weight is placed atop the stack, and the entire assembly is placed in a 50 C./35% relative humidity oven for 18 hours. The plates separate easily upon removal from the oven. This test simulates summer warehousing and transportation conditions; the ready separation of the plates indicates that little or no blocking will occur under those conditions.

(4) Another two of the coated aluminum plates are immersed in deionized water in a 50 C. oven for 18 hours. The plates are removed, stacked crosswise to form a 2.52.5 cm overlap area, wrapped in a wet paper towel, placed in a closed plastic bag, and then compressed in a press under a force of about 62 MPa for about six hours. The plates are firmly adhered to each other when removed from the press. Some delamination can be observed when the plates are pulled apart with sufficient force, which indicates that the strength of the coating-coating bond exceeds that between the coating and substrate.

EXAMPLES 2-7

(5) Plaques 2-5 are made by curing mixtures of an 85 equivalent weight, trifunctional glycerine-initiated poly (propylene oxide) polyether polyol, a 3.0 functional, 136 equivalent weight polymeric MDI and a catalyst at 80 C. for 30 minutes. The isocyanate index is as set forth in Table 1. Solid, non-cellular polymers are obtained in each case. The main glass transition temperature is measured as before. The wet aged glass transition temperature is measured for Examples 4 and 5. Results are as indicated in Table 1.

(6) Plaques 6 and 7 are made by curing mixtures of a 4.5-functional, 156 equivalent weight poly(propylene oxide) polyol with a 3.0 functional, 136 equivalent weight polymeric MDI at a 0.653 index or 0.745 index, respectively, at 80 C. in the presence of a catalyst. As before, solid, non-cellular polymers are obtained. Dry and wet aged glass transition temperatures are as indicated in Table 1.

(7) TABLE-US-00001 TABLE 1 Example No. 2 3 4 5 6 7 Isocyanate index 0.725 0.650 0.575 0.250 0.653 0.745 Main T.sub.g 103 90 69 43 45 55 Wet Aged T.sub.g ND ND 35 26 26 29

(8) The glass transition temperatures of these materials are suitable for use in the method of the invention. As demonstrated by Examples 4-7, these materials exhibit a significantly lower wet aged glass transition temperature, similar to Example 1.