DE3704802A1 - Process for modifying the mechanical properties of polyurethane foams - Google Patents

Abstract

In order to modify the mechanical properties - in particular in order to increase the strength and modulus - of polyurethane foams, the chemical starting materials of these foams are admixed with a finely particulate mineral additive. The particles thereof, as a constituent of the cell structure, cause, after curing, an increase in strength and modulus of the foam, dependent on the amount of admixed additive but without the inherent foaming behaviour of the pure foam being impaired. The additive can be gypsum, cement, crushed rock, quartz sand, etc.

Description

The invention relates to a method of change the mechanical properties of Polyurethane foams, thanks to the mineral Aggregates the bulk density of this Foams and their strength and their module can be changed without the rest of the characteristic of these foams Properties are lost.

The mechanical properties and characteristics of Polyurethane foams are said to be cheap mineral aggregates their respective Application purpose and to the extent can be changed as it is by chemical Additives to the raw materials of these foams cannot be reached.

Polyurethane foams are created by chemical Reaction of a polyol with a polyisocyanate. The low molecular weight, liquid raw materials network through the chemical reaction to a high molecular material. in the generally serves carbon dioxide, which is in the Reaction mixture forms as a leavening agent. Dependent of the desired mechanical properties of the foam to be produced the raw materials further liquid additives added (e.g. trichlorofluoromethane and tertiary amines).

The strength and modulus of a foam are largely dependent on its bulk density. This is due to the fact that the power transmission in a foam only takes place via its usable scaffolding. The Foam structure is composed of the Cell skins, cell webs and cell nodes. Both conventional foams Bulk density - and thus also strength and modulus - from the wall thicknesses of the (solely from the networked Existing) cell skins, - Bridges and knots, the different Training the wall thicknesses of the Foam structure due to the chemical formulation of the starting materials and possibly other liquid additives (e.g. trichlorofluoromethane and tertiary amines) is effected.  

The disadvantages of this method are that

• 1. a change in mechanical Properties of a foam over the Change in wall thickness (formed from the Foam material itself) of its cell structure occurs, which is bound to be a change its "foaming volume" entails; d. H. the ratio increases with increasing wall thickness between volumes of liquid raw materials and the foam volume obtained from it (when cured) lower.
• 2. increasing the bulk density - and thus strength and module - a foam one Limit is set. It is reached where the framework proportion of the foam due to ever thicker wall thicknesses of the cell substance such a large share of the "foaming volume" takes up the typical features and Properties (e.g. with regard to thermal insulation) of a "Foam" fabrics no longer exist are.
• 3. to change the mechanical properties and characteristics of a foam the starting materials according to the desired one Foaming and scaffolding behavior in each case special, different chemical additives are to be mixed.

The object of the present invention is to achieve this underlying a process for changing the mechanical properties of polyurethane To develop foams that oppose the usual

• 1. a change in mechanical properties and characteristics of the foams without Guaranteed impact on their "foaming volume".
• 2. the increase in strength and modulus of Allows foams to significantly higher values without doing the other typical Characteristics and properties of the foams too change.
• 3. a continuous change in strength and module of the foams.
• 4. the change in mechanical properties and characteristics of the foams with the help an inexpensive one for every foam formulation suitable aggregate enables.

To solve this problem, the chemical Starting materials for the polyurethane foams mineral aggregates added.

By stirring in the powder / flour mineral aggregate (e.g. gypsum, Cement, stone powder, fine quartz sand, etc.) in the liquid raw materials of the foams creates a mixture in which the mineral Aggregate is evenly distributed. In the chemical reaction becomes the particles of the Aggregate in the mixture from which the Builds up cell structure, part of the cell structure of the foam. When using such raw materials, their chemical formulation on a foam with low bulk density only the admixture leads mineral aggregates to the intended change in mechanical Properties, which is the "pure" raw material get peculiar "foaming volume" remains. Doing so will increase thickening required by the strength and modulus the wall thickness of the cell structure of the Foam only by the amount embedded particles of the admixed mineral aggregate in the Foam-forming chemical components causes. The physical structure of the load-bearing The structure of the cell structure thus consists of solid particles of the aggregate, which after their curing from the chemical foam components are glued together. The admixable Amount of aggregate is through the assets of the chemical Foam components, the particles of the aggregate to be able to glue together limited. This saturation is already evident when mixing in the aggregates. she is reached when the pasty mass of the mixture more powder / flour-like aggregate cannot record.

The interference of the mineral aggregates in the raw materials of the foam done in the following ways:

• 1. especially in one or the other Starting material, which means that each is loaded Component with increasing amount of aggregate an increasingly viscous to one dough-like consistency.  
• 2. during the mixing of the starting materials, whereby the reactive mix up charged with additives for saturation can be. This will make the highest possible Strength values of the foam reached.

The advantages brought about by this invention consist in that

• 1. with this type of physical structure the cellular structure of a foam values for Bulk densities and compressive strengths are achieved, like with conventional foam structures cannot be represented.
• 2. Foams with mineral additives even with the highest possible strength and highest possible module in contrast to corresponding conventional foams their favorable properties z. B. with regard to thermal insulation keep it. Are they also consider conventional foams clearly superior to sound insulation.
• 3. Foams with mineral additives compared to conventional foams without other special additives (e.g. flame retardants) fire retardant and self extinguishing Have properties.
• 4. The manufacturing costs for foams below Use of the very inexpensive mineral Aggregates turn out to be significantly less than those for foams with corresponding ones - comparatively expensive - chemical additives.
• 5. the through the use of mineral aggregates achievable mechanical properties of foams this a number open up new areas of application.

Claims (1)

Process for changing the mechanical properties of polyurethane foams, characterized in that a mineral additive (e.g. gypsum, cement, stone powder, quartz sand) is added to the chemical starting materials of these foams.