DE19958526A1 - Polyurethane adhesive useful especially for laminating applications is derived from polyisocyanate component and polyester-polyol component based on hydroxy-carboxylic acids, especially lactic acid - Google Patents

Abstract

Polyurethane adhesive derived from (A) polyester-polyols and (B) polyisocyanates, in which (A) are based on 2-5C hydroxy-carboxylic acid(s).

Description

The invention relates to a polyurethane adhesive made of polyester and polyols Polyisocyanates.

Polyurethane adhesives based on polyester polyols and polyisocyanates have been known for a long time.

Lactic acid-based diols have also been used for at least 10 years known. So in EP 0 250 994 their preparation, for. B. from ethylene glycol and lactic acid. It also suggests the flowable up solid oligomeric esters of lactic acid or their dermatologically compatible ones Derivatives as resorbable carriers and / or film formers for the production of a cosmetic or pharmaceutical agent for covering undamaged and / or use injured areas of human or animal skin. As Derivatives are called esters. There is no question of urethanes, nor of use of the polyester diols based on lactic acids in the adhesive Area.

The inventors set themselves the task, polyester diols did not petrochemical in nature, but based on renewable raw materials, especially plant-based for the production of polyurethane adhesives To make available or the polyurethane adhesives produced therefrom. In addition, appropriate use should also be found.

The solution of the invention can be found in the patent claims. It consists of primarily in the form of a polyester polyol, a polyester polyol based on  Hydroxycarboxylic acids with 2 to 5 carbon atoms, especially based on To use lactic acid for the production of the polyurethane adhesive.

Lactic acid is technically used in extraction and fermentation processes at Lactic acid fermentation, e.g. B. from milk and whey or from glucose and maltose Molasses and malt are widely produced. The starting product is mainly corn. Lactic acid or its derivatives are converted into Polymerization produced the polylactic acid (polylactide). That can e.g. B. by direct esterification with at least dihydric alcohols, by transesterification of lactic acid esters or by ring opening of lactide. The lactic acid is preferably reacted simultaneously or thereafter with suitable low molecular weight polyols the polylactic acid with several OH Groups. Suitable low molecular weight polyols are e.g. B. ethylene Glycol, propane-diol-1,2, propanediol-1,3, butanediol-1,3, butanediol-1,4, butanediol-2,3, Neopentylglycol, 1,6-hexanediol, hydroquinone, resorcinol and polyvalent Alcohols, especially glycerin and monoglycerides. Of course you can too low molecular weight polyalkylene diols or triols are used, e.g. B. Tripropylene glycol. Due to the molar ratio of lactic acid to the low molecular weight polyol, the molecular weight of polylactic acid with determined several OH groups. Polyester-based diols are preferred of lactic acid, in particular oligomers based on lactic acid with two OH end groups. The manufacturing conditions in detail are expressly stated refer to EP 0 250 994.

Further hydroxycarboxylic acids which can be used according to the invention are: glycolic acid, Hydroxybutyric acid and hydroxyvaleric acid.

The polyester polyols based on hydroxycarboxylic acids with 2 to 5 C- Serve atoms, especially lactic acid with two or more OH end groups according to the invention as a starting material for the production of polyurethanes Reaction with polyisocyanates. But you can also use it to make others Resins are used. The polyurethanes can be made from one or several polyester polyols and one or more polyisocyanates getting produced.  

Under a "polyisocyanate" is a low molecular weight compound with two or understood more isocyanate groups. The diisocyanates are preferred. she but can contain up to about 10 wt .-% of trifunctional isocyanates. In addition to aliphatic and cycloaliphatic polyisocyanates, above all aromatic polyisocyanates in question. In particular, as concrete examples called TDI and MDI.

In the case of polyester polyurethanes, one can differentiate between whether there is still one reactive or a non-reactive mass is to be applied. The reactive mass can in turn be differentiated between a polyester Polyurethane with still reactive NCO groups that react with water vapor (One-component system) and a system in which a polyester polyol (Resin) mixed with a polyisocyanate (hardener) immediately before application will (two-component system). The polyester according to the invention Polyurethanes made from polyester polyols based on lactic acid are suitable practically for all applications that are known for previously known polyester All types of polyurethanes are known. Express to the use for Gluing, coating and sealing (including casting compounds). The polyester polyurethanes according to the invention are particularly suitable for Glue. Here too, in principle, are all known adhesions of substrates possible. However, the use for lamination in should be emphasized Form of a two-component system.

Laminating becomes the binding of two or more layers of the same or understood different materials. These are papers, Textiles, plastics, metals and other materials that can be used as layers or Have foils processed. These materials are mostly in a calender in a rolling process under pressure with the polyester according to the invention Polyurethane bonded.

The polyester polyurethanes according to the invention based on polyester Lactic acid polyols showed surprisingly high despite the low viscosity Strength values and are therefore particularly suitable for lamination.  

They are environmentally friendly, and not just because they are made from renewable resources Raw materials, but also because they are biodegradable.

The invention will now be explained in detail using an example:
Analogously to Example 1c) of EP 0 250 994, a bifunctional oligo-lactic acid ester was produced from tripropylene glycol and ethyl lactate in a molar ratio of 1: 8.1. The viscosity was 836 mPas at 20 ° C (Haake rotary viscometer VT 500, spindle set MV1).

This reaction product was used as a resin in a ratio of 1: 1.2 with MDI as a hardener for laminating a 12 µm thick stretched film Polypropylene and a 50 µm thick film made of polyethylene are used.

The adhesive application was 3 µm.

After storage for 7 days at 20 ° C and 50% relative humidity curing ends. The bond adhesion was then 2.4 N / 15 mm, the Polypropylene film tore. The seal seam adhesion was 38 N / 15 mm, with a Compound demolition occurred.

Claims (5)

1. polyurethane adhesive made of polyester polyols and polyisocyanates, characterized in that the polyester polyol is based on at least one hydroxycarboxylic acid having 2 to 5 carbon atoms. 2. Polyurethane adhesive according to claim 1, characterized in that the Polyester-polyol is a poly-diol. 3. Polyurethane adhesive according to claim 1, characterized in that the Polyester-polyol a polymer, especially an oligomer preferably is the lactic acid with 2 primary and / or secondary OH end groups. 4. Polyurethane adhesive according to claim 1, characterized in that it is two-component and the resin component from at least one Polyester-polyol based on hydroxycarboxylic acid with 2 to 5 carbon atoms and the hardener component from a polyisocyanate, in particular one Diisocyanate exists. 5. Use of the polyurethane adhesive according to at least one of the Claims 1 to 4 for lamination.