CS198727B1 - Method for the stabilization of polyurethan foams microcell structure during preparation thereof - Google Patents

Description

(54) Method of stabilizing the microcell structure of polyurethane foams at the time of their preparation

The present invention solves a method of stabilizing the microcell structure of polyurethane foams at the time of their preparation using petroleum jelly. In particular, it is directed to novel types of cell structure stabilizers of polyurethane integral foams.

In the last Rococo period, the integral polyurethane foam has found wide application in the industry, which by compactness of the outer layer expanded the application possibilities of traditional use of polyurethane foams. The integral foam increases the durability of the polyurethane foams, improves the mehanogenic properties, and reduces the number of manufacturing operations during manufacture, while achieving the desired final product shape.

As is well known, the technology for producing polyurethane integral foams consists in accurately mixing the two fluid streams and pouring the homogenized mixture into the cavity of the heated mold. One of the reaction streams is referred to as isocyanate and consists either of chemically pure diisocyanate or of a mixture of polyols with an excess of diisocyanate with a certain amount of free isocyanate groups. The second reaction stream is referred to as the so-called. a polyel component which consists of a polyether polyester or a polyether polyol having a molecular weight of 1 to 4.10, a low molecular weight aiol, a blowing agent, a catalyst and a foam stabilizer.

And it is the composition of the foam stabilizers, their addition to the reaction mixture, as well as their concentration, that play an important role in ensuring proper stabilization of the gas cells.

198 727 during the production of polyurethane foam.

Among the many surfactants cited in the patent literature as cell size and stabilizer stabilizers in the manufacture of expanded polyurethanes are copolymers based on silicoses and propylonoxides, optionally ethylene oxides, adducts of nonylphenol and ethylene oxide, alifoxilanes, polyysilylphosphates, polyysilylphosphates, polyysilylphosphates. Thus, all the products of demanding ohmic synthesis, which are expensive and adversely affect the resulting economic roles of manufacturing processes.

In some literature, the use of paraffin oils as stabilizers of polyurethane foams is described. These oils are not able to fit into polyurethane blends with high resistance to mechanical stress at low temperatures, of the order of -20 ° C. So needed for a shoe shoe shop. For these purposes, oils with a high content of naphthenic hydrocarbons, the uses described in The literature is not, with the physical properties mentioned in the description of the invention, which are decisive for the achievement of the technical effect by the person according to the invention.

Polyurethane foam stabilizers have wetting and emulsifying properties. In particular, their role is to reduce the surface tension of the solution. When added in an amount below a certain critical range, cells become very unstable, gradually merging, subsequent boiling and foaming fail. When the stabilizer is used in an amount above the upper limit, the foam reaches the desired height and then sits down. This is explained by the formation of very tiny cells, the walls of which are thin and of low strength, which are not sufficient to maintain their shape when the gas begins to cool.

A disadvantage of said stabilizers is their weak emulsifying effect, which is manifested in particular by the pr. long time insoláoie. The premixed mixture of isocyanate and polyol component tends to separate the components. This phenomenon is observed, in particular, with the composition having a foaming time of more than 45 'seconds

These drawbacks are eliminated if, as a stabilization of the microcell structure of the polyurethane foams at the time of preparation, the process according to the invention is characterized in that deeply refined mineral oils prepared by multiple acid refining of aromatic oil distillate and aromatic paraffin oil are introduced into the polyurethane mixture. in the amount of 0.1 to 1.5 parts by weight of petroleum oils per 100 parts by weight of polyurethane foam.

The technical effect of the method according to the invention is that a uniform distribution of the size of the gas cells is achieved. The resulting polyurethane foam is fine »uniform. Even at higher dosages, coarse and stiff foam is not obtained. The softness of the foam suggests that petroleum oil, predominantly with naphthenic hydrocarbons, has excellent bubble nucleation capability that it has sufficiently cured by reducing the post tension. The uniformity of the foam in turn indicates a good emulsifying ability of petrolatum oil for polyols and isocyanates. This emulsifying ability is also excellent for slow reaction mixtures in which the start time is greater than 45 β. In addition to these advantages, undemanding low-temperature stabilizers from the group of silicone-propylene oxide copolymers have to be added.

In the production process, the formation of urethane foam begins by mixing together several reactants, which are often insoluble with each other. Mixing is accompanied by nucleation of gas bubbles, followed immediately by the initiation of a series of complex chemical reactions. In fact, foaming starts when the gas exits the solution and forms discrete cells. The energy required to create a new gas-liquid interphase is directly proportional to the surface tension and the flat gas interphase.

In addition, petroleum jelly oils also exhibit surface activity, induce nucleation by destroying surface tension while ensuring the stabilization of foam cells. Petroleum jelly oil as a surfactant is most effective in this respect when added directly to the polyol component mixture. The composition of petrolatum oil provides a reduction of the surface tension in a fraction of a second, immediately as the components are mixed, which is particularly needed in the so-called " ultra-rapid mixtures, which are used in particular in the manufacture of molded polyurethane products by the in-situ method, since the use of an elevated level of catalysts produces all or most of the gas in the first few seconds of the foaming cycle. Once bubbles have formed in the polyurethane foam system, they must be stabilized until the cellular structure has reached sufficient strength due to the polymerization. Between nucleation of the bubbles and the gelation of the polymer, the mass is continuously expanded and the individual bubbles must resist considerable shear stress in the manufacture of molded moldings in closed molds as the reaction mixture overcomes a large path for foaming the mold cavity.

Although all that has been said to be generally applicable to all known polyurethane foam stabilizers, the very good ability of the petroleum oils with a high content of naphthenic hydrocarbons used according to the invention to stabilize the masses in particular is applied in these sections. The chemical composition of these petrolatum oils ensures good surface elasticity and plasticity of the resulting polyurethane foam.

Petroleum jelly is predominantly colorless and odorless, deeply refined mineral oils produced by multiple acid refining of oil distillate, with predominantly naphthenic hydrocarbons for use as stabilizers of the microcell structure of the polyurethane foams at the time of their preparation. They are thus products of chemical processing of oil in which carbon is present in aromatic and paraffin-based, but in particular in naphthenic-chemical chemistry. For use according to the invention, the following physical properties are required for petrolatum oils:

Density (20 ° C) 0.870 to 0.880

Kinematic viscosity / ° C, cSt 22 to 49

Flash point in open crucible, ° C 130 to 140

Acid number mg KOH / g 0 to max. 0.03

Ash,% max. 0.003 to 0.01

Their amount in relation to 100 parts by weight of the polyurethane mixture is 0.1 to 1.5 parts by weight, which guarantees optimal effect according to the invention. When the proportion of petroleum oils in the polyurethane mixture exceeds 1.5 parts by weight, they are nucleated the effects do not greatly increase, although the increased dosage which might occur, for example, due to the failure of the metering device, does not affect the deterioration of the physical-meo-fire properties of the final products.

In the following description, petroleum oils will be used as stabilizers of the microcell structure of the polyurethane foams in accordance with the invention in more detail by way of example.

Example 1

A polyurethane foam with a microcell structure was prepared from the following components:

Diphenylmethyisocyanate modified with an ether alcohol in mol. weight of 2000 so as to contain 18% of the free -N00 groups 50 wt. d. Linear polyether prepared from adipic acid with butanediol in mol. weight 2000 41,069 wt. d. butanediol 8.5 wt. d. Crystalline triethylenediamine 0.23 wt. d. Petroleum oil 0.1 wt. d. Water 0.20 wt. d. dibutyltin 0.008 wt. d.

According to the above formulation, an early modified diphenylmethane diisocyanate is prepared which does not react with the other ingredients of the formulation. This gives a polyurethane material with a microcell structure which, at a density of 600 kg / m 3, has the following physical properties.

Tensile strength 6.9 MPa

Module 100 2.17 MPa

Tažnosí 470%

Tear strength 19.5 N / mm

Hardness 65 ° ShA

Example 2

Similar to Example 1, the following ingredients are used:

Polyether alcohol diphenylmethane diisocyanate with mol. weight 2000 so that it contains 15.4% free -N00 groups of 50 wt. d.

λ _m - 4. Λ ΙΛΛΛ J 'IZJ -i - ^Λ '

butanediol 7.4 game. d. Triohlórfluórmetan 3.7 wt. d. x / Petroleum oil 0.5 wt. d. A solution of triethylenediamine in dipropylene glycol, 33% 0.3 wt. d. dibutyltin 0.25 wt. D

According to the above reoepture, a modified diphenylmethane diisocyanate containing 15.4% free -NCO groups is first prepared. This represents a single reaction. The second stream consists of a mixture of the other components of the reoepture.

By reacting the two mixtures, a polyurethane microcell material is obtained which, at a weight of 600 kg / m 3, has the following physical-meo-fire properties:

Tensile strength 5 »50 MPa

Tear strength 15.50 N / mm

Tažnosí 430%

Hardness 68 ° Sh A

Example 3

It corresponds to the number of components and their proportions in parts by weight of Example 1, except that the polyether alcohol content of 4000, prepared from propylene oxide, corresponds to 31.35 parts by weight, and the petroleum oil content predominantly of naphthenic hydrocarbons corresponds to 1.5 parts by weight. The physicochemical values of the final microcell polyurethane foam product remain the same as the microcell structure of the polyurethane composition in Example 2.

χ / Petroleum processing product containing carbon in aromatic paraffinic but predominantly in a naphthenic or hemi-phenylene bond with a density of 0,870 to 0,880 / 20 ° C and with a flash point of 130 to 140 ° C in an open crucible.

OBJECT OF THE INVENTION

Claims (1)

OBJECT OF THE INVENTION Λ Process for stabilizing the microcell structure of polyurethane foams at the time of preparation using petroleum oils, characterized in that deeply refined mineral oils prepared by multiple acid refining of an oil distillate containing an aromatic and paraffinic but predominantly naphthenic carbon content are introduced into the polyurethane mixture. up to 1.5 parts by weight of petroleum oils per 100 parts by weight of polyurethane foam.