DE102010018434A1 - One-component adhesive, useful assembly adhesive for bonding absorbent and non absorbent substrates, comprises silane-terminated polymer, which is solvent-free, and cross-linked under the influence of moisture without foam - Google Patents

Abstract

One-component adhesive comprises a silane-terminated polymer, which is solvent-free, and cross-linked under the influence of moisture without foam and exhibits a Shore D (durometer) hardness of 40 in its hardened state according to a DIN 53505.

Description

The invention relates to a one-component adhesive based on a silane-terminated polymer, which is substantially solvent-free and crosslinks under the influence of moisture without foaming, and its use as a mounting adhesive for bonding absorbent and non-absorbent substrates.

For assembly bonding, adhesives based on aqueous dispersions have been used for decades. In addition to the advantage of freedom from solvents, however, the dispersion adhesives have various disadvantages. For example, they adhere poorly to substrates that are not absorbent. Apart from the limited range of adhesion, there are also problems due to shrinkage during curing. In addition to the solvent-free dispersion adhesives, thixotropic, solvent-borne contact adhesives are commonly used. The solvent content is not only disadvantageous in terms of the environment and the health of the user, but can lead to flammability and limited material compatibility. As assembly adhesives also one-component polyurethane adhesives (1-K-PUR adhesives) are still used. However, these release carbon dioxide on curing and therefore foam, which leads to swelling of the curing adhesive. In addition, the masses contain potentially carcinogenic ingredients, which is why from 1 December 2010 after the 30th adaptation of the Directive 67/548 / EEC ( Directive 2008/58 / EC ) in conjunction with Commission Regulation (EC) No 790/2009 of 10 August 2009 amending Regulation (EC) No 1272/2008 of the European Parliament and of the Council on the classification, labeling and packaging of substances and mixtures for the purpose of adaptation to technical and scientific progress (GHS Regulation) as isocyanate-containing preparations with R phrase 40 "Limited evidence of a carcinogenic effect". Another problem of the 1-component PU adhesives is their low color stability under the influence of UV radiation. Finally, one-component silane-terminated MS polymers are known which, however, only achieve comparatively low bond strengths of at most 5 N / mm ² for elastic adhesive joints and a hardness of up to 75 (Shore A).

There is therefore a need for a thixotropically adjustable one-component adhesive composition which has good adhesion to both absorbent and non-absorbent materials, is largely solvent-free and, according to the new GHS regulation in Class R40, free of labeling, while having a short setting time, during curing shows very low shrinkage or increase in volume, UV-stable if possible and forms tough-elastic adhesive joints with high tensile shear strengths in the cured state. The object of the invention is to provide such an adhesive.

The solution of this object succeeds with the one-component adhesive according to claim 1. The one-component adhesive according to the invention is based on a silane-terminated polymer, is essentially solvent-free and crosslinked under the influence of moisture without foaming. When cured, it has a Shore D hardness ( DIN 53505 ) of at least 40. The hardness of the cured adhesive composition according to the invention is substantially higher than in the hitherto commonly used silane-terminated adhesive systems. For example, it is significantly higher than that of the known STP (MS) polymers. The comparatively very high hardness leads to tough-elastic adhesive joints, which give durable bonds even under heavy external loads.

The adhesives of the invention are essentially solvent-free, which means that they contain less than 3% by weight, based on the total amount of the one-component adhesive, of volatile organic compounds (VOC) according to the EU VOC Solvent Emission Directive 1999/13 / EC Commission included. Preferably, the adhesive contains at most 1 wt .-%, and more preferably no volatile organic compounds.

The polymer on which the adhesive of the invention is based is a silane-terminated polymer. Its use ensures that the adhesive does not foam during curing, since no gas is generated during the curing process. Preference is given to using alkoxysilane-terminated polymers, for example methoxysilane-terminated, in the course of which methanol is formed. Since the alcohols formed in the crosslinking are pH-neutral, the adhesives of the invention can also be used in acid- or base-sensitive substrates.

As the backbone of the silane-terminated polymer used, a polyurethane is preferably used. However, other polymer chains are conceivable, for example polyethers. Polymers with a polyurethane backbone have the advantage of particularly good adhesion to a wide variety of substrates. Among the silane-terminated polyurethane polymers, the aliphatic polymers are preferred, since they have a particularly good UV resistance. Particularly preferred are - preferably aliphatic - polyether polyurethanes and in particular polyurethanes based on an (aliphatic) polyether and isophorone diisocyanate (IPDI). Preferred polyurethane polymers are isocyanate and silicone-free. Suitable polymers are for example in the EP 1093482 B1 or the US 6,884,852 B1 described.

In order to achieve the desired high hardness and a good bond strength, preference is given to using silane-terminated polymers having a comparatively low molecular weight. Preference is given to those polymers which have a molecular weight of at most 10,000 g / mol and more preferably have a molecular weight in the range from 4,000 to 6,000 g / mol.

The one-component adhesive according to the invention exhibits a very high initial strength, expressed as tensile shear strength ( DIN EN 1465: 2009-07 ), of at least 0.5 N / mm ² , this property preferably being reached at least 45 minutes after application of the one-component adhesive at room temperature. This means that a high bond strength is given already after a very short time. Even in the cured state - which means in the context of this application that is measured after 7 days of storage at room temperature - the one-component adhesive has extremely advantageous properties, namely, for example, a tensile shear strength ( DIN EN 1465: 2009-07 ) of at least 5 N / mm ² . Thus, very high bond strengths are achieved with tough-elastic adhesive joints. Another advantageous property is the good heat resistance. It amounts to WATT 91 ( DIN EN 14257 ) at least 6.5 N / mm ² .

Other desirable properties such as high UV stability, a suitable viscosity, thixotropy, etc. can be adjusted specifically by adding conventional additives. The one-component adhesive according to the invention therefore preferably additionally comprises at least one of the following components: an inorganic filler, in particular chalk, a crosslinker and / or adhesion promoter, a drying agent, a rheology modifier, a UV stabilizer, an antioxidant and a moisture-crosslinking reactive organic binder. The latter is used according to the invention to achieve a high initial strength of the adhesive composition. Suitable for this purpose are, for example, polymers with hydrolyzable end groups. Of these, particularly preferred are hydrolysable end groups which are activated via an α-effect, since these crosslink considerably faster than unactivated ones. In addition, no catalyst, in particular no tin catalyst, is needed for their crosslinking. As the polymer backbone of the reactive organic binder, for example, a polyether skeleton can be used. Suitable such compounds are, for example, in DE 10237271 A1 and EP 1529071 B1 described.

In the following, suitable quantitative ranges are given for the preferred components of the one-component adhesive according to the invention:
silane-terminated polymer: 10 to 40% by weight, preferably 20 to 30% by weight,
inorganic filler: 0 to 70 wt.%, preferably 10 to 60 wt.%, particularly preferably 30 to 60 wt.
Crosslinkers and / or adhesion promoters: 1 to 5 wt.%, Preferably 2 to 4 wt.
Desiccant: 0.5 to 3 wt .-%, preferably 1 to 2.5 wt .-%,
Rheology modifier: 0 to 5% by weight, preferably 1 to 3% by weight,
UV stabilizer: below 1 wt%,
Antioxidant: less than 1 wt%,
moisture-crosslinking reactive organic binder: 5 to 15 wt .-%, preferably 7 to 10 wt .-%.

• – 20 bis 30 Gew.-% silanterminiertem Polymer,
• – 30 bis 60 Gew.-% anorganischem Füllstoff,
• – 1 bis 5 Gew.-% Vernetzer und/oder Haftvermittler,
• – 0,5 bis 3 Gew.-% Trockenmittel,
• – 0 bis 5 Gew.-% Rheologiemodifikator,
• – unter 1 Gew.-% UV-Stabilisator sowie
• – 5 bis 10 Gew.-% feuchtigkeitsvernetzendem reaktiven organischen Bindemittel.

Particularly preferred adhesive compositions according to the invention have no further ingredients other than those listed below. In particular, neither plasticizer nor solvents are included. The one-component adhesive according to the invention accordingly consists of

• 20 to 30% by weight of silane-terminated polymer,
• From 30 to 60% by weight of inorganic filler,
• 1 to 5% by weight of crosslinker and / or adhesion promoter,
• 0.5 to 3% by weight of desiccant,
• 0 to 5% by weight of rheology modifier,
• - Under 1 wt .-% UV stabilizer and
• 5 to 10% by weight of moisture-crosslinking reactive organic binder.

An example of a composition according to the invention will be given below.

example

• – 32 Gew.-% Trimethylsilan-terminiertes Polyurethan-Polymer auf Basis von Polyether und IPDI, Molekulargewicht 4000–6000 g/Mol,
• – 56 Gew.-% anorganischer Füllstoff, Kreide (Omyalite 95 T)
• – 2,5 Gew.-% Vernetzer und/oder Haftvermittler (Dynasylan DAMO)
• – 2 Gew.-% Trockenmittel (Dynasylan VTMO)
• – 2 Gew.-% Rheologiemodifikator, pyrogene Kieselsäure (Cabosil TS 720)
• – 0,5 Gew.-% UV-Stabilisator (Tinuvin PUR 866)
• – 5 Gew.-% feuchtigkeitsvernetzendes reaktives organisches Bindemittel (Polyether mit durch α-Effekt aktivierten hydrolysierbaren Alkoxysilylgruppen).

In vacuo, the following components are uniformly mixed together to form a flowable mass:

• 32% by weight of trimethylsilane-terminated polyurethane polymer based on polyether and IPDI, molecular weight 4000-6000 g / mol,
• - 56 wt .-% inorganic filler, chalk (Omyalite 95 T)
• 2.5% by weight of crosslinker and / or adhesion promoter (Dynasylan DAMO)
• 2% by weight desiccant (Dynasylan VTMO)
• - 2% by weight rheology modifier, fumed silica (Cabosil TS 720)
• 0.5 wt.% UV stabilizer (Tinuvin PUR 866)
• - 5 wt .-% moisture-crosslinking reactive organic binder (polyether with activated by α-effect hydrolyzable alkoxysilyl groups).

The resulting mass is packed in a polyethylene cartridge with exclusion of air. It can be stored in the unopened cartridge for at least 9 months and can be applied by squeezing it out. The mass adheres to virtually all absorbent and non-absorbent substrates (except non-pretreated polyolefins). It cures with virtually no shrinkage or swelling. Measurements of the cured adhesive gave a tensile shear strength ( DIN EN 1465: 2009-07 ) of at least 5 N / mm ² , a Shore D hardness ( DIN 53505 ) of greater than 40 and a heat resistance according to WATT 91 ( DIN EN 14257 ) of more than 6.5 N / mm ² .

The measurements were in each case carried out according to the specifications of the specified DIN standards. In the case of measurement of tensile shear strength, the sample was prepared as follows: The one-component adhesive is uniformly applied with a mouth spatula to two test pieces of beech wood 150 × 20 × 5 mm dusted with a nonwoven fabric. Using a toothed spatula, the adhesive is peeled off perpendicular to the beech test specimen. Immediately thereafter, the adhesive film is evenly moistened by spraying it once with water from an atomizer bottle. Subsequently, the specimens are pressed together in a press first with low pressure, then increasing the pressing pressure to 6 bar, until the adhesive has set. Thereafter, the sample is taken out of the press and stored at 20 ° C and 50% RH for 7 days (or 45 minutes when measuring the initial strength) for a long time. To measure the tensile shear strength, the sample is then clamped vertically and stress-free in the tensile testing machine and then torn to breakage.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1093482 B1 [0007]
• US 6884852 B1 [0007]
• DE 10237271 A1 [0010]
• EP 1529071 B1 [0010]

Cited non-patent literature

• Directive 67/548 / EEC [0002]
• Directive 2008/58 / EC [0002]
• DIN 53505 [0004]
• DIN EN 1465: 2009-07 [0009]
• DIN EN 1465: 2009-07 [0009]
• DIN EN 14257 [0009]
• DIN EN 1465: 2009-07 [0015]
• DIN 53505 [0015]
• DIN EN 14257 [0015]

Claims (9)

One-component adhesive based on a silane-terminated polymer, which is substantially solvent-free and crosslinks under the influence of moisture without foaming, characterized in that it has a hardness according to Shore D (DIN 53505) of at least 40 in the cured state. One-component adhesive according to claim 1, characterized in that the silane-terminated polymer is an alkoxysilane-terminated polymer, preferably a silane-terminated polyurethane polymer, in particular a preferably aliphatic polyether polyurethane, particularly preferably a polyurethane based on a preferably aliphatic polyether and isophorone diisocyanate ( IPDI). One-component adhesive according to claim 1 or 2, characterized in that the silane-terminated polymer has a molecular weight of at most 10,000 g / mol and preferably a molecular weight in the range of 4,000 to 6,000 g / mol. One-component adhesive according to one of claims 1 to 3, characterized in that it has a tensile shear strength (DIN EN 1465: 2009-07) of at least 0.5 N / mm ² no later than 45 minutes after application. One-component adhesive according to one of claims 1 to 4, characterized in that it has at least one of the following properties in the cured state: - a tensile shear strength (DIN EN 1465: 2009-07) of at least 5 N / mm ² , - a heat resistance after WATT 91 (DIN EN 14257) of at least 6.5 N / mm ² . One-component adhesive according to one of claims 1 to 5, characterized, that it additionally comprises at least one of the following components: An inorganic filler, in particular chalk, A crosslinker and / or adhesion promoter, A desiccant, A rheology modifier, A UV stabilizer, - an antioxidant, A moisture-crosslinking reactive organic binder, in particular a polymer having hydrolyzable end groups, preferably hydrolysable end groups activated via an α-effect, particularly preferably a polyether with hydrolyzable end groups. One-component adhesive according to claim 6, characterized, that the components are contained in the following quantities: Silane-terminated polymer: 10 to 40% by weight, preferably 20 to 30% by weight, Inorganic filler: 0 to 70% by weight, preferably 10 to 60% by weight, particularly preferably 30 to 60% by weight, Crosslinking agents and / or adhesion promoters: 1 to 5% by weight, preferably 2 to 4% by weight, Desiccant: 0.5 to 3% by weight, preferably 1 to 2.5% by weight, Rheology modifier: 0 to 5% by weight, preferably 1 to 3% by weight, UV stabilizer: less than 1% by weight, Antioxidant: less than 1% by weight, Moisture-crosslinking reactive organic binder: 5 to 15% by weight, preferably 7 to 10% by weight. One-component adhesive according to claim 7, characterized, that he consists of 20 to 30% by weight of silane-terminated polymer, From 30 to 60% by weight of inorganic filler, 1 to 5% by weight of crosslinker and / or adhesion promoter, 0.5 to 3% by weight of desiccant, 0 to 5% by weight of rheology modifier, - Under 1 wt .-% UV stabilizer and 5 to 10% by weight of moisture-crosslinking reactive organic binder. Use of the one-component adhesive according to one of claims 1 to 8 as a mounting adhesive for bonding absorbent and non-absorbent substrates.