Polyurethane adhesive for cross-linked rubber bonding

Abstract

Disclosed herein is a two-component polyurethane adhesive system that includes a mixture of primary and secondary diamines.

Description

[Technical field]

[0001] The present disclosure relates to polyurethane-based two-component adhesives. [Background technology]

[0002] Polyurethane adhesives provide good adhesion to a variety of substrates, including crosslinked elastomeric materials. However, polyurethanes undergo significant weakening at higher temperatures. Vulcanized elastomers may be exposed to temperatures above 100°C in many applications, often under high loads. To achieve higher strength (defined as tear strength and high modulus), high T g Chain extenders are added to provide hard segments. Typical chain extenders include low molecular weight diols, diamines, amino alcohols and water. However, there is still a need to develop polyurethane adhesives with improved peel strength at higher temperatures, such as temperatures above 82°C. Summary of the Invention [Means for solving the problem]

[0003] In this specification, Ingredient A and Component B A two-component polyurethane adhesive system comprising: Ingredient A comprises (i) at least a first polyol, (ii) a primary diamine, and (iii) a secondary diamine; and Component B comprises a prepolymer that is a reaction product of at least one polyisocyanate and at least a second polyol, the primary diamine content level being: Ingredient A and the combined content level of the primary diamine and secondary diamine is about 10-30 wt % based on the total weight of the two-component polyurethane adhesive system.

[0004] In one embodiment of the two-component polyurethane adhesive system, Ingredient A and Component B is a weight ratio of about 1:5 to 5:1.

[0005] In a further embodiment of the two-component polyurethane adhesive system, Ingredient A teeth, Ingredient A The composition contains about 15 to 23 weight percent of a secondary diamine based on the weight of the composition.

[0006] In yet another embodiment of the two-component polyurethane adhesive system, the primary diamine is selected from the group consisting of dimethylthiotoluenediamine (DMTDA), methylenedianiline, diethyltoluenediamine, phenylenediamine (1,4-diaminobenzene), 4,4'-diaminobiphenyl, diaminonaphthalene, and combinations of two or more thereof.

[0007] In yet another embodiment of the two-component polyurethane adhesive system, the secondary diamine is selected from the group consisting of N,N'-di-sec-butyl-p-phenylenediamine (DSB-PDA), 4,4'-methylenebis[N-sec-butylaniline] (DSB-MDA), N-alkylated primary aromatic diamines, and combinations of two or more thereof.

[0008] In yet another embodiment of the two-component polyurethane adhesive system, the first polyol has a functionality of about 2-7 and an average equivalent weight of about 50-8000 g / mol.

[0009] Further provided herein is an article comprising a first substrate, a second substrate, and the two-component polyurethane adhesive system provided above, wherein the two-component polyurethane adhesive system is disposed between the first and second substrates.

[0010] In one embodiment of the article, one or both of the first and second substrates are formed from a crosslinked elastomer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] In this specification, Ingredient A and Component BA two-component polyurethane adhesive system is provided which is formed from two components: Ingredient A comprises at least one polyol and a mixture of primary and secondary diamines, as disclosed herein, while Component B comprises a prepolymer that is the reaction product of at least one polyisocyanate and at least one polyol. Ingredient A teeth, Ingredient A and the adhesive system comprises about 10-30 weight percent of a mixture of primary and secondary diamines, based on the total weight of the two-component polyurethane adhesive system.

[0012] Polyols as used herein include, but are not limited to, polyether polyols, polyester polyols, poly(alkylene carbonate) polyols, polybutadiene polyols, hydroxyl-containing polythioethers, and mixtures thereof. In one embodiment, the polyols as used herein are polyether polyols that contain one or more alkylene oxide units in the backbone of the polyol. Exemplary alkylene oxide units include ethylene oxide, propylene oxide, butylene oxide, and mixtures thereof. The alkylene oxide may contain linear or branched chain alkylene units. In embodiments where a mixture of alkylene oxide units is included in the polyol, the various units may be randomly arranged or may be arranged in respective blocks of alkylene oxide. In certain embodiments, the polyols as used herein may be diols, triols, or mixtures of diols and triols.

[0013] According to the present disclosure, Ingredient A The polyols included in may have a functionality of about 2 to 7, or about 2 to 5, or about 2 to 3, and an average equivalent weight of about 50 to 8000 g / mol, or about 50 to 4000 g / mol, or about 80 to 2000 g / mol. Ingredient A About 35 to 65% by weight or about 40 to 60% by weight of polyol based on the weight of the Ingredient A may be included in

[0014] Mixtures of primary and secondary diamines are also available. Ingredient A Preferably, the primary and secondary diamines used herein are aromatic diamines. Suitable primary diamines used herein include, but are not limited to, dimethylthiotoluenediamine (DMTDA), methylenedianiline, diethyltoluenediamine, phenylenediamine (1,4-diaminobenzene), 4,4'-diaminobiphenyl, diaminonaphthalene, and the like, while suitable secondary diamines used herein include, but are not limited to, N,N'-di-sec-butyl-p-phenylenediamine (DSB-PDA), 4,4'-methylenebis[N-sec-butylaniline] (DSB-MDA), N-alkylated (methylated, ethylated, sec-butylated) primary aromatic diamines of any of the above, and the like. Ingredient A about 7-19% by weight of a primary diamine and about 15-23% by weight of a secondary diamine based on the weight of the Ingredient A provided that the combined content level of primary and secondary diamines ranges from about 10 to 30 weight percent based on the total weight of the two-component polyurethane adhesive system.

[0015] According to the present disclosure, Component BThe polyisocyanates used in forming the prepolymers are polyfunctional isocyanates (e.g., diisocyanates and triisocyanates) and may be aliphatic, cycloaliphatic or aromatic polyisocyanates. Exemplary polyisocyanates for use herein include, but are not limited to, ethylene diisocyanate, hexamethylene-1,6-diisocyanate (HDI), isophorone diisocyanate (IPDI), 4,4'-, 2,2'- and 2,4'-dicyclohexylmethane diisocyanate (H12MDI), norbornene diisocyanate, 1,3- and 1,4-(bisisocyanatomethyl)cyclohexane (including its cis- or trans-isomers), tetramethylene-1,4-diisocyanate (TMXDI), These include 1,12-dodecane diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,2'-, 2,4'- and 4,4'-methyldiphenyl diisocyanate (MDI), carbodiimide modified MDI, 2,4- and 2,6-toluene diisocyanate (TDI), 1,3- and 1,4-phenylene diisocyanate, 1,5-naphthylene diisocyanate, triphenylmethane-4,4',4''-triisocyanate, polyphenylpolymethylene polyisocyanate and polymeric compounds thereof. In one embodiment, the polyisocyanate used herein is an oligomeric or polymeric isocyanate having aromatic groups. In further embodiments, the polyisocyanate used herein is selected from 2,2'-, 2,4'- and 4,4'-methyldiphenyl diisocyanate (MDI), carbodiimide modified MDI, 2,4- and 2,6-toluene diisocyanate (TDI), 1,3- and 1,4-phenylene diisocyanate, 1,5-naphthylene diisocyanate, triphenylmethane-4,4',4''-triisocyanate, polyphenylpolymethylene polyisocyanate and polymeric compounds thereof. In yet other embodiments, the polyfunctional isocyanate used herein is MDI or polymeric MDI.

[0016] Component BThe polyisocyanates used herein may have a percent NCO content of up to about 75%, or up to about 50%, or up to about 35%. For example, the percent NCO content may range from about 20-75% or from about 28-34%. In certain embodiments, the polyisocyanates used herein may have an average isocyanate functionality of at least about 2, or at least about 2.2, or at least about 2.4 and about 4 or less, or about 3.5 or less, or about 3.2 or less. In further embodiments, the equivalent weight of the polyisocyanate may be at least about 100, or at least about 110, or at least about 120, and about 300 or less, or about 250 or less, or about 200 or less.

[0017] Component B The polyol used in forming the prepolymer in can be any suitable polyol described above. In one embodiment, Component B The polyol used in is a polyether diol. The prepolymer can be formed by the application of heat, the addition of a catalyst, or a combination of both, by methods known to those skilled in the art. The prepolymer can have a viscosity of less than about 20,000 cPs at room temperature, or less than about 10,000 cPs at room temperature, or less than about 8000 cPs at room temperature. The molecular weight of the polyol, the functionality of the polyol, and the weight percent of the polyol in the prepolymer are selected to produce a prepolymer having an isocyanate content of about 2-27 weight percent, or about 5-20 weight percent, or about 10-20 weight percent.

[0018] moreover, Ingredient A , Component B Or carbon black may be incorporated in both compositions. In one embodiment, about 6-15% by weight of carbon black is incorporated into the two-component adhesive system.

[0019] moreover, Ingredient A , Component BAdditional additives may be added in either or both compositions, including, but not limited to, catalysts, plasticizers, crosslinkers, fillers, moisture scavengers, colorants, heat stabilizers, etc. In particular, a number of aliphatic and aromatic amines (e.g., diaminobicyclooctane-DABCO), organometallic compounds (e.g., dibutyltin dilaurate, dibutyltin diacetate), alkali metal salts of carboxylic acids and phenols (calcium, magnesium, strontium, barium salts of hexanoic, octanoic, naphthenic, linolenic acids) may be used as catalysts.

[0020] According to the present disclosure, Ingredient A and Component B The compositions are prepared and stored separately until use. Ingredient A and Component B The compositions are mixed in a weight ratio of about 1:5 to 5:1, or about 1:4 to 4:1, or about 1:2 to 2:1.

[0021] As demonstrated by the following examples, Ingredient A By adding a mixture of primary and secondary diamines, the resulting two-component adhesive system exhibits much improved peel strength to crosslinked elastomeric materials.

[0022] Further provided herein is a method for applying a two-component adhesive system between two substrates to form a bonded structure. In one embodiment, one or both of the two substrates are formed from a crosslinked elastomer, such as vulcanized rubber. Typically, Ingredient A and Component B are mixed and then the adhesive system is applied between the substrates and subsequently cured at ambient temperature. The present invention includes the following aspects. Section 1. Ingredient A and Component B A two-component polyurethane adhesive system comprising: Ingredient A comprises (i) at least a first polyol, (ii) a primary diamine, and (iii) a secondary diamine; and Component Bcomprises a prepolymer that is the reaction product of at least one polyisocyanate and at least a second polyol; The content level of the primary diamine is Ingredient A About 7 to 19% by weight based on the total weight of A two-component polyurethane adhesive system, wherein the combined content level of the primary diamine and the secondary diamine is about 10-30 wt %, based on the total weight of the two-component polyurethane adhesive system. Section 2. Ingredient A and Component B The two-component polyurethane adhesive system according to item 1, wherein the weight ratio of the polyurethane is about 1:5 to 5:1. Section 3. Ingredient A teeth, Ingredient A Item 2. The two-component polyurethane adhesive system according to item 1, comprising about 15 to 23 weight percent of said secondary diamine, based on the weight of said system. Section 4. Item 2. The two-component polyurethane adhesive system of item 1, wherein the primary diamine is an aromatic diamine. Section 5. Item 2. The two-component polyurethane adhesive system according to item 1, wherein the primary diamine is selected from the group consisting of dimethylthiotoluenediamine (DMTDA), methylenedianiline, diethyltoluenediamine, phenylenediamine (1,4-diaminobenzene), 4,4'-diaminobiphenyl, diaminonaphthalene, and combinations of two or more thereof. Section 6. Item 2. The two-component polyurethane adhesive system of item 1, wherein the secondary diamine is an aromatic diamine. Section 7. Item 2. The two-component polyurethane adhesive system according to item 1, wherein the secondary diamine is selected from the group consisting of N,N'-di-sec-butyl-p-phenylenediamine (DSB-PDA), 4,4'-methylenebis[N-sec-butylaniline] (DSB-MDA), N-alkylated primary aromatic diamines, and combinations of two or more thereof. Section 8. Item 2. The two-component polyurethane adhesive system according to item 1, wherein the first polyol has a functionality of about 2-7 and an average equivalent weight of about 50-8000 g / mol. Section 9. Item 7. An article comprising a first substrate, a second substrate, and the two-component polyurethane adhesive system according to any one of items 1 to 6, wherein the two-component polyurethane adhesive system is disposed between the first and second substrates. Section 10. Item 10. The article of item 9, wherein one or both of the first and second substrates are formed from a crosslinked elastomer. EXAMPLES

[0023] material Polyol-1 - capped polyether triol (functionality: 3; MW: 4610 g / mol), obtained from Dow Inc. under the trade name VORANOL™ 232-036N; Polyol-2 - polyether triol (functionality: 3; MW: 254 g / mol), obtained from Dow Inc. under the trade name VORANOL™ 230-660; · Polyol-3 - a liquid hydroxyl-terminated polymer of butadiene (functionality of 2.5, MW: 1300 g / mol), obtained from Cray Valley USA, LLC under the trade name Poly bd™ R-20LM; · Polyol-4 - a propylene glycol based polyether polyol diol (functionality: 2; MW: 2000 g / mol), obtained from Dow Inc. under the trade name VORANOL™ 220-056N; · DMTDA - available from Albemarle under the trade name ETHACURE™ 300 Curative, a primary diamine dimethylthiotoluenediamine (DMTDA); · DSB-PDA - available from Dorf Ketal, LLC under the trade name UNILINK™ 4100, a secondary diamine N,N'-di-sec-butyl-p-phenylenediamine (DSB-PDA); · DSB-MDA - available from Dorf Ketal, LLC under the trade name UNILINK™ 4200, a secondary diamine 4,4'-methylenebis[N-sec-butylaniline] (DSB-MDA); · P-MDI - available from Dow Inc. under the trade name PAPI™ 27, polymeric MDI (polymethylene polyphenylisocyanate containing MDI); · CB - carbon black, obtained from Cabot under the trade name ELFTEX™ S7100; Defoamer - available from Dystar under the trade name FOAM BLAST™ 20F.

[0024] Ingredient A : Each embodiment Ingredient A For the 100% ethanol ...

[0025] Component B : In each embodiment, Component B was prepared as follows: The following ingredients were first mixed at 47°C: P-MDI (1996 g); Polyol-4 (1366 g); Defoamer (0.26 g); and Dimethyltin Carboxylate (14.64 g of a 2.43 wt% solution in diisononyl phthalate). Diisononyl phthalate (90.6 g); Diethyl malonate (35 g); and 4,4'-(Di-2,1-ethanediyl)bismorpholine (DMDEE, 2.64 g) were then added to the mixture and mixed at 60°C. After the mixture was cooled to room temperature, CB (dried overnight in an oven at approximately 200-204°C) was added to the mixture at 10 wt% and the resulting dispersion was mixed using a Flaktek high speed mixer.

[0026] Peel Strength: Vulcanized rubber strips (a blend of polybutadiene (BR) and styrene butadiene (SBR)) were roughened on a belt sander and the surface was activated using a chemical oxidant, a 2% by weight solution of trichloroisocyanuric acid in ethyl acetate in these examples. After the solution was allowed to dry for at least 5 minutes, the coupon surfaces were wiped with an organic solvent, in these examples toluene. In each example, a Flaktek high speed mixer was used to mix 100% ethylenediaminetetraacetate (EDTA) and 100% ethylenediaminetetraacetate (EDTA). Ingredient A and Component B was mixed and applied between two 2 inch wide strips of vulcanized rubber (a blend of polybutadiene (BR) and styrene butadiene (SBR)) and the test assembly was placed in a vacuum with active vacuum applied for 2-4 hours. The test assembly was then removed from the vacuum bag and stored at 75°F and 50% RH for 20-22 hours and T-peel tested on an Instron at 82°C and a peel rate of 2 inches / minute. The average and maximum peel strengths were obtained and are summarized in Table 1.

[0027] Examples E1 to E8 and Comparative Examples CE1 to CE8: As demonstrated herein, the adhesive systems E1 to E8 each have Ingredient A % or more by weight of a primary diamine in the A+B adhesive system and about 10% or more by weight of a primary and secondary diamine in the A+B adhesive system, such adhesives show much improved peel strength compared to the adhesives CE1-CE8.

[0028] [Table 1]

Claims

1. A two-component polyurethane adhesive system comprising component A and component B, Component A comprises (i) at least a first polyol, (ii) an aromatic diamine having two primary amines, and (iii) an aromatic diamine having two secondary amines; and Component B comprises a prepolymer that is a reaction product of at least one polyisocyanate and at least a second polyol, the prepolymer having an isocyanate content of 2 to 27 weight percent; the content level of the aromatic diamine having two primary amines is 7 to 19 wt %, based on the total weight of component A; the content level of the aromatic diamine having two secondary amines is 15 to 27 wt. %, based on the total weight of component A; the combined content level of said aromatic diamine having two primary amines and said aromatic diamine having two secondary amines is 10-30 wt. %, based on the total weight of said two-component polyurethane adhesive system; A two-component polyurethane adhesive system, wherein Part A and Part B are in a weight ratio of 1:4 to 4:

1.

2. 2. The two-component polyurethane adhesive system of claim 1, wherein the aromatic diamine having two primary amines is selected from the group consisting of dimethylthiotoluenediamine (DMTDA), methylenedianiline, diethyltoluenediamine, phenylenediamine (1,4-diaminobenzene), 4,4'-diaminobiphenyl, diaminonaphthalene, and combinations of two or more thereof.

3. 2. The two-component polyurethane adhesive system of claim 1, wherein the aromatic diamine having two secondary amines is selected from the group consisting of N,N'-di-sec-butyl-p-phenylenediamine (DSB-PDA), 4,4'-methylenebis[N-sec-butylaniline] (DSB-MDA), N-alkylated primary aromatic diamines, and combinations of two or more thereof.

4. 2. The two-component polyurethane adhesive system according to claim 1, wherein the first polyol has a functionality of 2 to 7 and a molar mass of 50 to 8000 g / mol.

5. 5. An article comprising a first substrate, a second substrate, and the two-component polyurethane adhesive system according to any one of claims 1 to 4, wherein the two-component polyurethane adhesive system is disposed between the first and second substrates.

6. The article of claim 5 , wherein one or both of the first and second substrates are formed from a crosslinked elastomer.

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