Polyurethane glass adhesive with reduced slip

Abstract

A novel primer-free adhesive composition having unique properties in automotive related applications, in particular in glass bonding applications; and a manufacturing method thereof.

Description

[0001] This application is a divisional application of application number "201780081962.6" filed on December 21, 2017, entitled "Polyurethane Glass Bonding Adhesives with Reduced Slippage".

[0002] The present invention relates to a new primerless adhesive composition with unique properties in automotive related applications, particularly in glass bonding applications.

[0003] A typical glass bonding adhesive kit contains a primer and a moisture-cured urethane adhesive. Glass bonding primers typically contain organic solvents, organosilane intermediates, isocyanate prepolymers, film formers, carbon black, catalysts, and stabilizers. The primer modifies the glass surface to make it bond well with the moisture-cured urethane adhesive. The isocyanate in the primer is subjected to moisture cure to produce a crosslinked thermoset network which makes the primer robust enough to have sufficient durability under environmental conditions. However, the primer must have sufficient crosslink density to withstand high temperature and high humidity conditions. As part of general simplification and process streamlining, many vehicle manufacturers have tried to eliminate the surface pretreatment step of using a separate primer composition. As such, the adhesive is intended to be applied directly to the glass or paint without a separate primer application step. A key requirement for such simplified applications is to establish the adhesion of the adhesive to the paint, e-coat, and glass so as to form a long lasting joint. It is important that the bonded glass does not slip out of the original position due to deformation of the adhesive or migration of the adhesive at the substrate interface. Slippage occurs mainly on the flat surfaces of glass and paint with low surface roughness.

[0004] Accordingly, it would be desirable to have a glass bonding adhesive composition that can be applied to a glass surface without a primer pretreatment and has little or no slippage after application. It would be further desirable that such an adhesive can be applied without any additional heating step. In other words, it would be desirable to have an adhesive that is flowable at cold or room temperature.

[0005] The present invention provides such a unique adhesive composition by carefully selecting the dosage of isocyanate and the dosage of 2,2'-dimorpholinodiethylether ("DMDEE") in the adhesive, such that the adhesive allows for application at cold or room temperature, exhibits minimal slippage when applied on flat glass, and provides good surface adhesion.

[0006] A typical adhesive composition of the present invention comprises A) a filler (which includes both AI and A-II (two filler types)), which may be one of the following: white pigment, carbon black, calcined kaolin, fumed silica, calcium carbonate, uncoated kaolin, or a mixture thereof; B) a glass bonding accelerator; C) one or more catalysts; D) a plasticizer; E) a prepolymer (including both EI and E-II prepolymers); F) an isocyanate; and G) a solvent or heat stabilizer. It is important to maintain the ratio of prepolymer to filler between 1.2 and 3.55, preferably between 1.6 and 3.0, and more preferably between 2.2 and 2.9, in order to achieve improved sliding properties (≤ 3.55%).

[0007] Different fillers can be used in different amounts. For adhesive compositions containing AI fillers, in typical embodiments, the adhesive composition may contain 10 to 26 wt.%, preferably 16 to 25 wt.%, and more preferably 18 to 23 wt.%, of carbon black, such as Printex, commercially available from Orion Carbons, based on the total weight of the adhesive composition. TM 30. In the case of A-II filler, the adhesive composition will typically contain 2 to 23 wt.%, preferably 5 to 18 wt.%, and more preferably 13 to 15 wt.%, of calcined kaolin, such as PoleStar commercially available from Imerys. TM 200R; and 13 to 17 wt.%, preferably 2 to 23 wt.%, and more preferably 5 to 13 wt.%, of uncoated kaolin, such as Carbital, commercially available from Erythrope Company. TM 120.

[0008] For glass bonding accelerators (“Component B”), such as Silquest, which is commercially available from Momentive. TM A187, A189, and A1170 should be used in amounts of less than 2.5 wt.%, preferably less than 1.6 wt.%, and more preferably less than 1.4 wt.%, all based on the total weight of the adhesive composition.

[0009] For Component C, the adhesive composition of the present application preferably comprises 0.1 to 1.6 wt.%, preferably 0.4-1.2 wt.% and more preferably 0.6 to 1.1 wt% of dimethyl-tin-dilaurate, such as Formrez UL28 commercially available from Dow Chemical Company (as a 2.4% solution in plasticizer DINP), and 0.2 to 0.6 wt.%, preferably 0.3 to 0.4 wt.% and more preferably 0.35 to 0.45 wt% of DMDEE, all based on the total weight of the adhesive composition. Optionally, an amine catalyst can also be used additionally to control the skinning time.

[0010] For Component D, the adhesive composition of the present application preferably comprises 0.1 to 50 wt.%, preferably 10 to 40 wt.% and more preferably 15 to 35 wt.% of diisononyl phthalate, such as Vestinol TM .

[0011] For Components E-I, it is important to keep the amount of prepolymers in the adhesive composition low in order to maintain the flowability of the adhesive composition at cold or room temperature. Thus, the adhesive composition of the present application preferably comprises 0.5 to 2.5 wt.%, preferably 0.8 to 1.8 wt.% and more preferably 1.0 to 1.5 wt% of a reaction product of a polyester polyol with diphenylmethane-4,4'-diisocyanate ("MDI"), such as prepolymer B.

[0012] Prepolymer B was prepared with the following method: by mixing 46.7 g of plasticizer reagent (a branched plasticizer), 30.15 g of isocyanate (diphenylmethane 4,4'-diisocyanate) commercially available from Dow Chemical Company under the trade name Isonate TM M125U, 190.0 g of polyester polyol commercially available from Evonik under the trade name DYNACOL TM 7381, a polyester polyol was prepared. The entire mixture was then stirred for 8 hours.

[0013] In addition to the above mentioned E-I prepolymers, another MDI / PPO (diphenylmethane-4,4'-diisocyanate / polypropylene oxide polyol) based prepolymer, such as prepolymer A (Component E-II) can also be included in the adhesive composition. The composition preferably comprises 55-60 wt.%, preferably 55.2 to 57 wt.% and more preferably 55.5 to 56 wt.% of such MDI / PPO based prepolymers. All weight percentages are based on the total weight of the adhesive composition.

[0014] Prepolymer A was prepared with this method: A polyether urethane prepolymer was prepared by mixing 22.3150 g of polyoxypropylene diol commercially available under the trade designation Voranol™ 2000L having an average molecular weight of 2000 g / mol with 33.9350 g of polyoxypropylene triol having an average molecular weight of 4650 g / mol and commercially available under the trade designation Arcol™ CP 4655. 34.1430 g of plasticizer reagent (linear plasticizer) was added. In addition, 9.5900 g of diphenylmethane 4,4'-diisocyanate was added. Then, 0.001 g of orthophosphoric acid in 0.009 g of MEK was added. Then, the whole mixture was heated to 50 °C in a reactor and 0.007 g of stannous octoate was added and.

[0015] For component F, the adhesive composition of the present invention comprises 0.1 to 3 wt.%, preferably 0.3 to 1.5 wt.% and more preferably 0.5 to 0.8 wt.% of hexamethylene diisocyanate trimer having an NCO content of about 21.8% commercially available from Covestro as Desmodur® N3300. All weight percentages are based on the total weight of the adhesive composition.

[0016] For component G, different solvents or thermal stabilizers can be used in different amounts. In a typical embodiment, the adhesive composition can comprise 0.05 to 5 wt.%, preferably 0.05 to 3 wt.% and more preferably 0.05 to 1 wt.% of diethyl malonate (DEM) commercially available from BASF, based on the total weight of the adhesive composition.

[0017] In a preferred embodiment, the ratio between component E-II and component A-II is between 1% and 3.55%, preferably between 2.5% and 3.55%, and more preferably between 3% and 3.55%.

[0018] The present invention can be further illustrated by the following non-limiting examples.

[0019] In order to illustrate the effectiveness of the present invention, a total of five examples were prepared according to Table 1. Two of them are examples of the present invention, while three of them are comparative examples.

[0020] Table 1. Examples and comparison with comparative examples

[0021] The above samples were prepared by mixing component E-II (PPO-based prepolymer A) with components B, C, D, F, and G. Component A filler, such as carbon black, calcined kaolin, and fumed silica, was added. The mixture was stirred for another five minutes under a nitrogen atmosphere. The mixture was then heated to 60°C. Component EI was added at 60°C, and the mixture was subsequently mixed under vacuum for 35 minutes. Then, components B and C, a small portion of component D (e.g., diisononyl phthalate), a tin catalyst, and an amine catalyst were added, and the mixture was stirred under vacuum for 15 minutes or until a homogeneous, paste-like black mixture (adhesive composition) was obtained.

[0022] The sliding resistance of the adhesive was tested after 24 hours. A sliding resistance of 10 mm was expected to be the allowable limit, and 5 mm was considered to be a good sliding resistance.

[0023] A sliding test was designed based on laboratory testing to ensure the sliding resistance of a vertically mounted windshield, and the test included the following steps: • Apply two parallel beads of the material to be tested (total approximately 12 g; triangular shape, 8 mm bottom and 14 mm (standard size) height) to a 190 x 90 mm (standard size) unprimed electrophoretic coated sample and check the correct weight of the applied adhesive beads. • Maintain a material application temperature of 23°C • After 3 minutes of application, assemble a 125 x 75 mm (standard size) unprimed glass plate to a thickness of 4 mm bead and hold it in place for 30 seconds. • Remove the spacer and rotate the assembly to a vertical position, securing a glass plate. Add weight to lower the glass sample until a total weight of 8 N is applied, and measure the slip after 1.5 hours. • Record all measurements and details of the material being tested. As shown in Table 2, Example 1 of the present invention demonstrates very good sliding resistance due to the very high amount of amine catalyst in DMDEE. Additionally, Example 2 of the present invention provides good, but higher, sliding resistance below the threshold (10 mm), due to a slight reduction in the amine catalyst content. Comparative Examples 3 and 4 show high sliding resistance due to the low amount of amine catalyst associated with skin formation. Comparative Example 5 shows slightly higher sliding resistance due to the higher amount of NCO- content (Isonate M600 + Desmodur® N3300). The higher NCO- content reduces the amine-catalyst / NCO ratio associated with curing rate / skinning time. This is presumably the reason for the reduced sliding resistance.

[0024] Table 2. Sliding Test Results

[0025] Specifically, the amine-catalyst content, the ratio of prepolymer to white pigment is varied to provide the best possible surface adhesion and best reduction in slip. In particular, the amine-catalyst required for fast skin-over time is combined with higher white pigment usage to result in low slip / high slip resistance on glass surfaces.

[0026] Comparative Examples 3 to 5 reflect the state of the art. They all do not have very low viscosity, very high G' (i.e. 1 x 10(6) Pa*s), or very high amounts of surface adhesion promoters, and the combination of these factors results in a very slippery glass surface slip-out of the adhesive. This slip reduction performance is particularly important for primerless adhesives that bond to glass when the ceramic frit glass coating is between two glass layers, and thus the adhesive must be placed directly on the glass surface.

Claims

1. An adhesive composition comprising A) at least one of the following: white pigment, carbon black, calcined kaolin, fumed silica, calcium carbonate, uncoated kaolin, or mixtures thereof; B) one or more glass bonding accelerators; C) one or more catalysts; D) a plasticizer; E) a prepolymer; F) an isocyanate; and G) a solvent or heat stabilizer.

2. The adhesive composition of claim 1, wherein, The prepolymer comprises the reaction product of polyester polyol and diphenylmethane-4,4'-diisocyanate.

3. The adhesive composition of claim 2, wherein, The composition comprises 0.5 to 2.5 wt.% of the reaction product of the polyester polyol and diphenylmethane-4,4'-diisocyanate based on the total weight of the composition.

4. The adhesive composition of claim 1, wherein, The catalyst contains 2,2'-dimorpholinodiethyl ether.

5. The adhesive composition of claim 4, wherein, The composition comprises 0.2 to 0.6 wt.% of 2,2'-dimorpholinodiethyl ether based on the total weight of the composition.

6. The adhesive composition of claim 1, comprising 0.1 to 3 wt.% of a hexamethylene diisocyanate trimer having an NCO content of about 21.8% based on the total weight of the composition.

7. The adhesive composition of claim 1, wherein, The ratio of prepolymer to filler is between 1.2 and 3.55.

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