EP3853296A1

EP3853296A1 - A polyurethane foam and production method thereof and a cooling device

Info

Publication number: EP3853296A1
Application number: EP19749692.0A
Authority: EP
Inventors: Tugce ONER; Orcun YUCEL; Yusuf YUSUFOGLU; Cahit Can CANAKCI; Sefa Yasin UZEN
Original assignee: Arcelik AS
Current assignee: Arcelik AS
Priority date: 2018-09-20
Filing date: 2019-07-31
Publication date: 2021-07-28
Also published as: WO2020057840A1

Abstract

The present invention relates to a polyurethane foam with improved thermal and mechanical properties comprising at least one polyol (polyol mixture) mixed with at least one surfactant and at least one catalyst and water, at least one cyclopentane or isobutane/cyclopentane as blowing gas and at least one isocyanate, also relates to the production method thereof and to a cooling device.

Description

A POLYURETHANE FOAM AND PRODUCTION METHOD THEREOF AND A COOLING DEVICE

The present invention relates to a polyurethane foam, to the production method of the polyurethane foam and a cooling device comprising the polyurethane foam.
Polyurethane foams have very good adiabatic properties. Thanks to their high thermal insulation properties, they are commonly used in building insulation in the construction sector and in cooling systems such as refrigerators, deep freezers, etc. The polyurethane foams are divided into the groups, which are hard and soft, and during the production stage, the main reaction occurs via the polyol mixed with isocyanate and blowing agent earlier on. Additionally, catalysts, nucleating agents, surfactants and other chemicals can be used as additives. Improving especially the thermal properties of the polyurethane foam is related to the total thermal conductivity coefficient. The insulation value of said material is increased by using components therein with low thermal conductivity coefficients.
The total thermal conductivity coefficient of polyurethane foams is represented by λ_total. Therefore; in the equation λ_total= λ_gas + λ_solid + λ_radiation, the gas component makes the highest effect, which is more than 60% to the total thermal conductivity coefficient. Said gas thermal conductivity vale (λ_gas) is directly related to the blowing agent added in to the polyurethane foam. The most common blowing agent today is cyclopentane. The most important reason of this is the minimum effect of the agent on ozone depletion and global warming. However, the thermal conductivity coefficient of the cyclopentane which is 12 mW/mK cannot meet the requirements of the systems with high energy efficiency which are increasingly used with each passing day. Therefore, in the polyurethane foams, the compounds are required to be improved with compounds in addition to the blowing agent, which in turn requires innovations.
In state of the art embodiments, the most common nucleating agents are used to increase the closed cell ratio in the polyurethane foam and to improve the thermal properties of the polyurethane foam so as to provide said developments. Thus, by increasing the closed cell ratio in the foam, the thermal properties of the foam are improved. However, the nucleating agents currently used cannot provide sufficiently effective solutions.
In the state of the art United States Patent Document no. US2016108236, it is disclosed that the mechanical properties of the polyurethane foam are improved with the additive of nanocrystalline cellulose.
In another state of the United States Patent Document No. US20170166682, a refrigerator is disclosed, characterized by the polyurethane foam having a hydroxyl group comprising nanosized and microsized linen fiber, cellulose fiber, etc.
The aim of the present invention is the realization of a polyurethane foam with improved material properties (thermal, mechanic, etc.), of the production method of said polyurethane foam, and of a cooling device comprising the polyurethane foam.
The polyurethane foam realized to attain the aim of the present invention, explicated in the first claim and the respective claims thereof comprises at least one surfactant and at least one catalyst and at least one polyol which is mixed with water and at least one cyclopentane or mixture of isobutane/cyclopentane and at least one isocyanate as blowing agent and microcrystalline cellulose as the nucleating agent. By means of the polyurethane foam of the present invention, mechanical properties such as thermal insulation performance and
To clarify the mixtures of the polyurethane foam and the production method of the present invention, some definitions will be given. These are as follows:
Base polyol: defines only the polyol.
Polyol mixture: defines a mixture comprising at least one polyol mixed with at least one surfactant and at least one catalyst and water.
A component: defines the polyol mixture and cyclopentane or polyol mixture and isobutane/cyclopentane mixture.
B component: defines the isocyanate compounds completing the reaction.
The microcrystalline cellulose in the polyurethane foam disperses in the polyurethane in an easy and homogeneous manner, and thus a material with equal properties at every region is obtained.
The polyurethane foam of the present invention comprises the surfactant which is 2% to 5% of the polyol mixture by weight. The surfactant in the polyurethane foam is about 2 to 3 times the catalyst by weight. Thus, a polyol mixture with a more homogeneous and fluid structure is obtained.
The polyol mixture in the first step of the production of the polyurethane foam comprises at least one of the blowing catalyst and/or gel catalyst and/or trimer catalyst or the mixture thereof.
The polyol mixture comprises at least one catalyst which is mixed by 0.5 to 5% by weight. Thus, the polyurethane foam is formed in a quick and efficient manner.
In the polyurethane foam of the present invention, conventional methylene diisocyanate as isocyanate component (B component). The use of methylene diisocyanate plays an important role in improving the mechanical properties, especially compressive strength, of the polyurethane foam.
In an embodiment of the present invention, the polyurethane foam comprises water which is 2% of the polyol mixture by weight. Thus, the components in the polyol mixture are enabled to easily disperse in each other.
The polyurethane foam of the present invention is used in cooling devices as insulation material.
The polyurethane foams are materials which are obtained by mixing the polyol, already mixed with cyclopentane, with isocyanate, and which are used as insulation material.
In order to improve and increase the insulation properties of the material, the polyurethane foam of the present invention comprises

at least one polyol (polyol mixture) mixed with at least one surfactant and at least one catalyst and water, and
at least one cyclopentane or isobutane/cyclopentane mixture as blowing agent, and
at least one isocyanate, and
microcrystalline cellulose as nucleating agent.

Thanks to the composition of the polyurethane foam of the present invention, cell formation in the polyurethane foam increases, and thus thermal conductivity is enabled to significantly decrease. Consequently, as the thermal conductivity coefficient decreases, a more efficient insulation is provided.
The base polyol is the main component required for the polyurethane foam reaction. In an embodiment of the present invention, polyether polyol or polyester polyol is used as base polyol. The use of said components provides ease of production and cost advantage.
In a preferred embodiment of the present invention, the surfactant in the polyol mixture in the polyurethane foam of the present invention is a siloxane-based surfactant which decreases the surface energy of the mixture, for the base polyol which has a molecular weight of 400-800 g/mol. By decreasing the surface energy, a more efficient polyol mixture is obtained. Moreover, by means of the use of the surfactant, the components in the polyurethane foam are enabled to be efficiently mixed. Thus, the components which are homogeneously mixed make a better contribution to the improvement of the thermal properties of the polyurethane foam.
In an embodiment of the present invention, the ratio of the surfactant is between 2% to 5%. Thus, the fluidity and thermal conductivity coefficient values of the resulting material are enabled to be optimum.
The catalysts in the polyol mixture in the polyurethane foam of the present invention are selected from at least one of the blowing catalyst and/or gel catalyst and/or trimer catalyst or the mixture thereof. By means of said catalysts, the reactions are performed in the desired time and conditions.
In the polyurethane foam of the present invention, metal-based catalysts are ignored, and amine-based catalysts are used as reaction catalyst. Said catalysts are selected from at least one of the bis(2-dimethylaminoethyl) (methyl) amine (C₉H₂₃N₃ based) and/or cyclohexyldimethylamine (C₈H₁₇N based) and/or N,N,N’,N’,N’’,N’’-Hexamethyl-1,3,5-triazine-1,3,5 (2H,4H,6H)-tripropanamine (C₁₈H₄₂N₆) or the mixture thereof.
The catalysts in the polyurethane foam of the present invention are 0.5% to 5% of the total polyol mixture by weight. The range given for said ratio enables the reaction to be performed with the desired efficiency and under desired conditions.
In a preferred embodiment of the present invention, the polyurethane foam of the present invention comprises Tegostab® as surfactant, Polycat® 5 as blowing catalyst, Polycat® 41 as gel catalyst and Polycat® 8 as trimer catalyst. The general advantage of the specific surfactant and catalysts used is to provide fluidity in the reaction, to accelerate the reaction in the desired time, and to enable the components to be mixed well.
In an embodiment of the present invention, the surfactant is 2-3 times the total catalyst weight. Thus, the materials in the components of the polyurethane foam are enabled to be mixed well, providing a desired fluidity value.
The water in the polyol mixture in the polyurethane foam of the present invention is used as mixing agent/solvent.
The polyurethane foam of the present invention comprises high-purity cyclopentane or isobutane/cyclopentane mixture as blowing gas. Thus, a closed cell ratio of 95% or above is obtained, and the insulation properties of the material are brought up to desired levels.
The B component is the component which provides the completion of the reaction for the A component (cyclopentane or isobutane/cyclopentane mixed with polyol mixture) with added microcrystal and which provides the curing of the polyurethane foam. In a preferred embodiment of the polyurethane foam of the present invention, the B component is the conventional methylene diphenyl isocyanate. By means of said component used, the polyurethane foam of the present invention is provided with a rigid structure.
In a preferred embodiment of the present invention, the polyurethane foam comprises 1.3-1.5 unit conventional methylene diphenyl diisocyanate in a 1 unit polyol mixture. Thus, the mechanical properties of the polyurethane foam material are optimized.
The polyurethane foam of the present invention comprises microcrystalline cellulose as nucleating agent. By means of the high effect value (length/width ratio) of the microcrystalline cellulose, the curing process of the polyurethane is accelerated and the polyurethane foam form is obtained more quickly. Moreover, by means of the homogeneous dispersion of the microcrystalline cellulose in the polyurethane, the pore dispersion of the material becomes homogeneous. Thus, a material with the same properties at every region is obtained.
The microcrystalline cellulose increases cell formation in the polyurethane foam of the present invention. Thus, the thermal conductivity decreases and the polyurethane foam gains better insulation properties.
In a preferred embodiment of the present invention, the effect value (length/width ratio) of the microcrystalline cellulose is 3:2 and the diameter thereof is between 0.6 to 1.5 microns. Said values provide the polyurethane foam with better thermal insulation properties, and contribute to the homogeneous mixing of the components.
In an embodiment of the present invention, the polyol mixture comprises, for 100 unit bas polyol, 2-2.5 unit surfactant, 0.4-1 unit blowing catalyst, 2-3 unit gel catalyst, 0.6-0.8 unit trimer catalyst and 1-2 unit pure water. The resulting polyol mixture is defined as 1 unit polyol mixture.
In this embodiment, in order to form the A component, 14-17 unit cyclopentane is added to the 1 unit polyol mixture. In said embodiment of the present invention, after the formation of the A component, 0.2 to 3 unit microcrystalline cellulose is added to the A component. Thus, by means of the microcrystalline cellulose added as nucleating agent, cell formation in the polyurethane foam is increased while the thermal conductivity is decreased. In said embodiment of the present invention, in the A component with added microcrystalline cellulose, 1.3-1.5 unit isocyanate is added to 1 unit polyol mixture, thus forming the polyurethane foam. With the components in said amounts in the polyurethane foam of the present invention, an optimum reaction is provided and the thermal properties of the material are improved (the thermal conductivity coefficient thereof is decreased).
The production method of the polyurethane foam of the present invention comprises the steps of
- preparing the polyol mixture comprising at least one surfactant and at least one catalyst and water,
- forming the A component by adding at least one cyclopentane or isobutane/cyclopentane mixture to the resulting polyol mixture,
- adding microcrystalline cellulose to the A component, and
- curing the polyurethane foam by adding at least one isocyanate compound to the A component and microcrystalline mixture.
By means of said method, a polyurethane foam with improved thermal insulation and homogeneous pore dispersion is obtained. By means of said method, a polyurethane foam with a compressive strength of 130 kPa-140 kPa can be obtained.
In the polyurethane foam production method, ultrasonification and/or gravitational and/or mechanical stirrers are used to efficiently mix the microcrystalline cellulose with the A component. In the method, in the mixing of the microcrystalline cellulose with ultrasonification, the thermal conductivity coefficient is improved by 0.7 mW/mK, while gravitational and mechanical mixings provide an improvement by 0.5-0.6 mW/mK.
In a preferred embodiment of the polyurethane foam production method, mechanical mixers with a rpm of 9000 are used. Thus, the microcrystalline cellulose is enabled to disperse well in the polyol mixture.
In an embodiment of the polyurethane foam production method of the present invention, by mixing 1 to 1.5 grams of microcrystalline cellulose into 100 grams of base polyol, the thermal conductivity values of the polyurethane foam are improved by 0.5-0.7 mW/mK.
The polyurethane foam of the present invention is used in cooling devices such as refrigerator, etc.
By means of the present invention, a polyurethane foam with improved compressive strength and thermal insulation properties is realized.

Claims

A polyurethane foam comprising at least one polyol (polyol mixture) mixed with at least one surfactant and at least one catalyst and water, and at least one cyclopentane or isobutane/cyclopentane mixture as blowing gas, and at least one isocyanate,

- characterized by comprising microcrystalline cellulose as nucleating agent.
A polyurethane foam as in Claim 1, comprising the microcrystalline cellulose with a length/width ratio (aspect ratio) of 3:2.
A polyurethane foam as in Claim 1 or 2, comprising the microcrystalline cellulose with a diameter of 0.6 to 1.5 microns.
A polyurethane foam as in any one of the Claims 1 to 3, comprising the siloxane-based surfactant which decreases the surface energy of the mixture for the base polyol which has a molecular weight of 400-800 g/mol.
A polyurethane foam as in Claim 4, comprising the surfactant which is 2% to 5% of the polyol mixture by weight.
A polyurethane foam as in Claim 4 or 5, comprising the surfactant 2 or 3 times the catalyst by weight.
A polyurethane foam as in any one of the Claims 1 to 6, comprising at least one of the blowing catalyst and/or gel catalyst and/or trimer catalyst or the mixture thereof.
A polyurethane foam as in Claim 7, comprising the catalyst selected from at least one of the bis(2-dimethylaminoethyl) (methyl) amine (C₉H₂₃N₃ based) and/or cyclohexyldimethylamine (C₈H₁₇N based) and/or N,N,N’,N’,N’’,N’’-Hexamethyl-1,3,5-triazine-1,3,5 (2H,4H,6H)-tripropanamine (C₁₈H₄₂N₆) or the mixture thereof.
A polyurethane foam as in Claim 7 or 8, comprising at least one catalyst which is mixed into the polyol mixture by 0.5% to 5% by weight.
A polyurethane foam as in any one of the Claims 1 to 9, comprising Tegostab® as surfactant, Polycat® 5 as blowing catalyst, Polycat® 41 as gel catalyst and Polycat® 8 as trimer catalyst.
A polyurethane foam as in any one of the Claims 1 to 10, comprising conventional methylene diisocyanate as isocyanate.
A polyurethane foam as in Claim 11, comprising 1.3 to 1.5 unit methylene diisocyanate for 1 unit polyol mixture.
A polyurethane foam as in any one of the Claims 1 to 12, comprising the 1 unit polyol mixture having, for 100 unit bas polyol, 2-2.5 unit surfactant, 0.4-1 unit blowing catalyst, 2-3 unit gel catalyst, 0.6-0.8 unit trimer catalyst and 1-2 unit pure water, and by 14-17 unit cyclopentane and 1.3-1.5 unit isocyanate and 0.2-3 unit microcrystalline cellulose for 1 unit polyol mixture.
A cooling device comprising a polyurethane foam as in any one of the above claims.
A polyurethane foam production method for forming polyurethane foam, comprising the steps of

- preparing the polyol mixture comprising at least one surfactant and at least one catalyst and water,

- forming the A component by adding at least one cyclopentane or isobutane/cyclopentane mixture to the resulting polyol mixture,

- adding microcrystalline cellulose to the A component, and

- curing the polyurethane foam by adding at least one isocyanate compound to the A component and microcrystalline mixture.