FR2678627A1 - PROCESS FOR THE MANUFACTURE OF ELASTOMERIC POLYURETHANS, PARTICULARLY IN THE FORM OF SHOE SOLE. - Google Patents

Abstract

Process for manufacturing elastomeric polyurethanes, in particular in the form of shoe soles, by reaction of a reaction mixture, intended to form polyurethanes, polyol, isocyanate, crosslinking agents and optionally catalysts, swelling agents and other mixed additives, characterized in that the polyol, isocyanate and crosslinker components are introduced via separate lines into a mixing chamber in which they are brought into contact with one another and mixed together.

Description

The present invention relates to a process for manufacturing polyurethanes

  elastomers, in particular in the form of shoe soles, by reaction of a reaction mixture, intended to form polyurethanes, consisting of a polyol, an isocyanate, crosslinking agents and optionally catalysts, swelling agents and other mixed additives Ce type of process is known from the document

EP-A-0 368 270.

  For the manufacture of elastomeric polyurethanes, the following are used as starting components: 1 of aromatic polyisocyanates such as those described for example by W Siefken in the document Justus Liebigs Annalen der Chemie, 562, pages 75 to 136, which correspond for example to the formula Q (NCO) n in which n represents a number from 2 to 4, preferably equal to 2, and Q represents an aromatic hydrocarbon residue from 6 to 15, preferably from 6 to 13 carbon atoms, for example of the type polyisocyanates

  described in document DE-A-28 32 253 on pages 10 and 11.

  In general, particularly preferred are technically easily accessible polyisocyanates, for example 2,4 and 2,6-toluylene diisocyanate as well.

  as any mixtures of these isomers ("TDI"), polyphenylpoly-

  methylene polyisocyanates such as those obtained by condensation of

  aniline and formaldehyde then phosgenation ("crude MDI") and polyisocya-

  nates comprising carbodiimide groups, urethane groups, allophanate groups, isocyanurate groups, urea groups or biuret groups ("modified polyisocyanates"), in particular modified polyisocyanates which are derived from 2,4 and / or 2,6toluylènediisocyanate or 4.4 'and / or

  2,4 '-diphenylmethanediisocyanate.

  2 The starting component is also the "polyol" component which can be represented for example by polyesters comprising at least two

  hydrogen atoms capable of reacting with isocyanates and present

  as a molecular weight generally between 400 and 10,000 These compounds are compounds which contain, in addition to amine, thiol or carboxyl groups, preferably hydroxyl groups, in particular 2 to 8 hydroxyl groups, and particularly compounds of a molecular weight of 1,000 to 8,000, preferably 2,000 to 4,000, for example compounds which have at least two hydroxyl groups, generally 2 to 8 hydroxyl groups, preferably 2 to 4 hydroxyl groups, such as the compounds which are known per se for

  the manufacture of homogeneous polyurethanes and cellular polyurethanes

  which are described for example in document DE-A-28 32253

on pages 11 to 18.

  According to the invention, polyethers, polycar-

  bonates, polylactones and polyamides with a molecular weight of 400 to 10,000 and

  which have at least two hydroxyl groups.

  3 The starting components are also crosslinking agents, that is to say compounds comprising at least two hydrogen atoms capable of reacting with isocyanates and which have a molecular weight of 18 to 399. type of compounds compounds which contain hydroxyl groups and / or amine groups and / or thiol groups and / or carboxyl groups, preferably compounds which contain hydroxyl groups and / or amine groups and which are used as agents Generally, these compounds contain 2 to 8, and preferably 2 to 4 hydrogen atoms capable of reacting with isocyanates. Examples of compounds of this type are described in the document.

DE-A-28 32253 on pages 19 and 20.

  4 Optionally, blowing agents such as water or

volatile compounds.

  Optionally, combustion retarders can also be used.

tion known per se.

  6 It is possible to use adjuvants and additives known per se,

  as emulsifiers and stabilizers Preferred as emulsifiers are

  fiants emulsifiers based on alkoxylated fatty acids and higher alcohol.

  Regarding stabilizers, these are mainly polyether-

  siloxannes, in particular of those which are water-soluble These compounds are generally constituted in such a way that a copolymer of ethylene oxide and

  of propylene oxide is bound to a residue of polydimethylsiloxane Des stabili-

  This type of rim is described, for example, in US Pat. Nos. 2,834,748, 2,917,480 and 3,629,308. The catalysts known in the art can also be used.

  itself in polyurethane chemistry, such as tertiary amines and / or

organometallic.

  Inhibitors can also be used, for example acid reaction substances, such as hydrochloric acid or organic acid halides, as well as regulators of cell formation of a type known per se, such as paraffins, alcohols oily or dimethylpolysiloxannes, as well as pigments or dyes, stabilizers against aging and

  bad weather, plasticizers, fungistatic and bacterio-

  static as well as fillers such as barium sulfate, earth

  diatomaceous earth, the black of smoke or the white of Meudon.

  The document Kunststoff-Handbuch, vol VII, edited by Vieweg and Hôchtlen, Carl-Hanser-Verlag, M nchen 1966, describes for example on pages 103 to 113 other examples of surfactant additives, foam stabilizers, regulators of formation of cells, inhibitors, stabilizers, retardants, plasticizers, dyes, fillers and fungistatic and bacteriostatic substances which can be used as well as

  details regarding the use and mode of action of these additives.

  The manufacture of shoe soles in elastomeric polyurethanes

  risk is generally carried out by direct injection on the upper For the production of the reaction mixture, we previously mixed

  a crosslinking agent, a catalyst and a blowing agent with the

  setting polyol This premix was then mixed with the isocyanate in a mixing head. The reaction mixture reacted to form a material with a compact to cellular appearance and soft to hard in the relative proportions of

polyol and crosslinking agent.

  Since such a premix is only moderately stable on storage, as indicated in document EP-A-0 368 270, column 1, lines 29 to 50, attempts have been made, as also indicated in this document, to remedy the poor storage stability, to carry out the premixing process only when the liquid level in the daily production tank falls below a predetermined minimum level, a limited amount of make-up being added during each premixing process, this quantity make-up through a heat exchanger before reaching the daily production tank to be heated to a temperature corresponding to the temperature of this tank However, this solution does not eliminate all the disadvantages For example, the side of the installation which is in contact with the mixture of polyol and crosslinking agent must be completely drained and cleaned during prolonged periods of rest, for example at the end of the week, since the chemical reaction between the polyol and the crosslinking agent occurs from the start, so that the transition from a satisfactory quality to a totally unusable quality is unclear and that an irreproachable production is only possible when the final transformation takes place immediately after the premixing process. However, the most serious drawback is that it is necessary to prepare a premix of polyol and other components among which

  the crosslinking agent plays the most important role Indeed, the crosslinking agent

  lation determines the degree of hardness of the elastomer or the sole of the shoe and this degree of hardness must be changed very often during the

  production During these modifications, there are normally residual quantities

  dual premixes which, if impossible to use within a period

  reasonable, become unusable because of the reactions which develop there.

  It is therefore necessary to imagine, for the manufacture of elastomeric polyurethanes, in particular in the form of shoe soles, a process which makes it possible to avoid the emptying processes on the polyol side of

  installation during prolonged exposures and which also allows modification

  immediate cation without loss of the degree of hardness of the elastomer.

  This object is achieved in that the components that are the polyol, the iso-

  cyanate and the crosslinking agent are introduced via separate lines into a mixing chamber in which they are brought into contact with each other.

others and mixed together.

  This measure makes it possible to avoid losses of polyol mixture and of crosslinking agent and of additional operations, compared to the previous process, since no premature reaction can occur. It is then possible to immediately and independently modify the polyol part, which determines the characteristics, and the crosslinking agent part, which is

responsible for the degree of hardness.

  The separate introduction of any individual components, for example colorants, into the mixing chamber is known per se.

  manufacture of elastomeric polyurethanes and in particular in the manufacture of

  shoe soles, there were prejudices against

  direct introduction of the crosslinking agent into the mixing chamber.

  Since on the one hand the shoe soles are relatively small molded parts and on the other hand that the proportion of crosslinking agent is very low compared to the polyol, it was considered impossible to guarantee an exact dosage of these small quantities from the first to the last millisecond In addition, it was considered that a homogeneous distribution of small quantities of this kind was only possible by a premix in the polyol In other words, it was believed that the direct introduction into the mixing chamber would not produce sufficient mixing and therefore an optimal end product

  for this particular application.

  Preferably, catalysts and / or blowing agents are likewise introduced separately which are only mixed with the other components.

in the mixing chamber.

  It is also verified for these additives that it is possible to carry out immediate modifications without loss thanks to their direct introduction into the mixing chamber. The modification of the proportion of catalyst causes a modification of the reaction time and the modification of the proportion of blowing agent causes a modification of the internal pressure of the material In the case of shoe soles having complicated contours, in particular, one must operate with relatively high foam pressures so that the contours of the mold cavity are

reproduced exactly.

  The fact that these prejudices are overcome also opens up other possibilities.

  unpredictable and surprising abilities such as the following: the processing temperature of the polyol can be increased appreciably This results in a significant drop in viscosity and therefore in a noticeable improvement in the quality of the mixture While it was common until now to use treatment temperatures of 25 to 50 ° C., according to the process of the invention, the operation is preferably carried out at temperatures of

  treatment of 60 to 150 'C, in particular 110' C, for the polyol.

  For the mixing, the usual methods of the technique of using polyurethanes are applied. Mixers with a stirring or screw system are used, for example, and the mixture is used by injection under high pressure, which makes it possible to prepare at the injection rate the

  quantity of mixture required per molded part.

Claims (3)

  1 Process for manufacturing elastomeric polyurethanes, in particular   binding in the form of shoe soles, by reaction of a reaction mixture, intended to form polyurethanes, polyol, isocyanate, crosslinking agents and optionally catalysts, swelling agents and other mixed additives, characterized in that that the polyol, isocyanate and crosslinking agents are introduced via separate lines into a mixing chamber in which they are brought into contact with each other the others and mixed together.   2 Method according to claim 1, characterized in that the catalysts and / or the blowing agents are also introduced separately and are not   mixed with the other components than in the mixing chamber.   3 Method according to claim 1 or 2, characterized in that the temperature   The treatment rate of the polyol component is chosen between 60 and 150 @C.