DE2418334A1 - METHOD OF LIQUID INJECTION MOLDING - Google Patents

Description

DIpL-lng. P. WIRTH Dr. V. SCHMIED-KOWARZIK DipWng. G. DANNENBERG Dr. P. WEINHOLD ■ Dr. D. GUDEL

281134 β FRANKFURTAM MAIN

TELEPHONE (0611)

287014 GR. ESCHENHEIMER STRASSE 39

SK / SK

Ref .: 150 I.P.R.C.

Inter-Polymer Research Corporation Building No. 5
Har ^ v-Real Industrial Park Farmingdale, New Jersey 07727 / USA

Process for liquid injection molding

The present invention relates to liquid injection molding of polyurethane elastomers as well as molded polyurethane elastomer articles obtained from liquid injection molding processes.

In the manufacture of thermoplastic, for injection molding Suitable polyurethane elastomers are a polyether diol or polyester diol with a molecular weight of about 2000 and a slow reacting alkylene glycol extender with an organic diisocyanate to form a solid linear polymer implemented. The linear polymer has a relatively low heat resistance and can therefore be used in the drum section a conventional injection molding machine currently in use. The melting of the polymer takes place through the frictional heat of the mixing screw, supported by an additional heat source, such as a wrapped around the drum of the mixing and molding machine

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Resistance coil.

The "one-shot" process for the production of polyurethane elastomers which are suitable for thermoplastic injection molding cannot use any more rapidly reacting extenders ¹¹ , such as the diamines and amino alcohols with reaction rates above that of the alkylene glycols, since the branched polymers obtained have one too. have high heat resistance to be melted in the manner described above. Furthermore, the method is rarely used because of the difficulty in balancing the reactions of the different components.

In the prepolymer process for casting liquid polyurethane elastomers, a polyether diol or polyester diol having a molecular weight of about 2000 is reacted with an organic diisocyanate to form a prepolymer having a ratio of free isocyanate groups to hydroxyl groups of 2: 1 or more. The prepolymer is mixed with a slowly reacting extender, such as an alkylene glycol or a hindered amine, such as methylenebis (orthochloroaniline) in a low-speed mixing and injection molding machine in a heated mold, in which the polymerization and curing then take place.

Like the "one-shot ¹¹ process, the prepolymer process cannot use faster reacting extenders for the liquid casting of the polyurethane elastomers, since otherwise the polymerisation in the mixing and injection molding plant would occur, which would be put out of operation. Therefore, one must react to the slower reacting Use extenders, which leads to longer curing

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cycles, which are clearly disadvantageous in the case of large-scale, expedient deformation systems.

The. produced by the "one-shot" and prepolymer process cured polyurethane elastomers often have relatively low heat strengths, which limits their field of application will.

The present invention now relates to a process for the liquid injection molding of polyurethane elastomers, daa is characterized in that one

a) a solution or dispersion of at least one polyether and / or bath Polyester diol with terminal hydroxyl groups, at least one organic bifunctional extender from the Group of diamines, amino alcohols or glycols with a reaction rate above that of the alkylene glycols or hindered amines and an effective amount of at least one catalyst for the polyurethane reaction with a prepolymer

Polyether and / or sat from the reaction of at least one / polyester diol with terminal hydroxyl groups or a mixture thereof with at least one organic diisocyanate to form a prepolymer combined with an average ratio of free isocyanate groups to hydroxyl groups above about 2: 1, the rate at which the above components are combined is sufficient to produce a practically homogeneous liquid Forming reaction mixture in which no noticeable polymerization occurred prior to the introduction of the mixture into the mold;

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b) introducing the liquid reaction mixture into a mold;

c) the mold contents of the molded polyurethane elastomer article hardens; and

d) the cured polyurethane elastomer article from the Shape removed.

The method according to the invention has the advantage over the known and customary liquid injection molding systems to be exceptionally quick and easy to control. Furthermore, the polyurethane elastomer articles obtained according to the invention have higher heat resistance, better resistance to solvents and oils and higher rigidity than

from mixtures

the previously known / liquid / injection-molded polyurethane elastomers.

Examples of polyether diols which are suitable according to the invention and which are terminated Hydroxyl groups include the linear or practically linear polyalkylene ether glycols derived from alkylene oxides, glycols, heterocyclic ethers and other materials by polymerization, interpolymerization, etc., are derived. E.g. Tetrahydrofuran in the presence of catalytic amounts of fluorosulfonic acid to form a polytetramethylene ether glycol of the formula

HO (CH ₂ CH ₂ CH ₂ CH ₂ O) _χ Η (I)

are polymerized, 'in which χ for one of the number of moles of converted tetrahydrofuran corresponding whole number. Ethylene oxide / propylene oxide mixtures, propylene oxide, etc. can be used to create other polyalkylene ether glycols. Glycols can in the presence of mineral acid, sulfonic acid or Fuller's earth are polymerized. Furthermore you can

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for the production of polyalkylene ether glycols the other known ones Procedures are applied.

These linear polyether glycols can be represented by the following formula:

HO (RO) _X H "(II)

in which R stands for an alkylene chain with at least 2 carbon atoms or an arylalkylene group and η is an integer. Furthermore, R can be a mixture of alkylene and / or Arylalkylene groups, e.g. alternating groups or blocks of ethylene and propylene residues, i.e. a polyethylene / polypropylene ether glycol, be. Examples of practically linear polyalkylene ether glycols are polyethylene propylene ether glycol, polyneopentylene ether glycol, Polyhexamethylene ether glycol, poly-4-phenylhexamethylene ether glycol, Poly-1,6-heptamethylene ether glycol etc. The polyethers suitably have a molecular weight of. around 2000, albeit with lower or higher polyethers Molecular weights can be used.

The hydroxyl-terminated polyester diols useful in the process of the present invention include polyesters having a molecular weight of about 2000, which are produced by reacting a dihydric alcohol with a dicarboxylic acid. In the Reaction with a dicarboxylic acid to form a polyester, any dihydric alcohol can be used, e.g. Ethylene glycol, propylene glycol, hexanediol, diethylene glycol, bis (hydroxymethycyclohexane), Polyethylene glycols, polypropylene glycols, etc. Any suitable dicarboxylic acid can be used,

such as.

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Adipic acid, succinic acid, suberic acid, sebacic acid, methyl adipic acid, Glutaric acid, pimelic acid, azelaic acid, bthalic acid, Terephthalic acid, isophthalic acid, thiodiglycolic acid, thiodipropionic acid, Maleic acid, fumaric acid, etc.

Lactone polyesters can also be used in the process of the invention terminal hydroxyl groups, expediently with a molecular weight of about 2000, characterized by recurring lactone units be used. These lactone polyesters include polyesters of individual unsubstituted and substituted lactones and copolyesters of substituted and unsubstituted lactones and mixtures thereof.

Any lactone or combination of lactones having at least 6 carbon atoms, e.g. 6-8 carbon atoms, can be used as the starting material in the ring and at least one hydrogen substituent on the carbon atom attached to the oxy group of this ring be used. The lactone used as the starting material can on the one hand by the following general formula being represented:

RCH (CR ₂ ) _n C = 0

0 1

in which η has a value of at least 4, for example 4 to 6, at least n + 2 substituents R stand for hydrogen and the remaining R is hydrogen, alkyl, cycloalkyl, alkoxy or individual aromatic ring hydrocarbon radicals. Lactones having a greater number of other substituents on the ring than hydrogen "and lactones having 5 or fewer carbon atoms in the Ring are unsuitable according to the invention because their polymers

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tend to revert to the monomers, especially at elevated temperatures.

The preferred lactones in the manufacture of hydroxyl terminated lactone polyesters are the ε. -Caprolactone the general formula:

RRRRR

I I t I I

H-C-C-C-C-C-C = O

I. I. I. ! R. R. R. R. 0-

in which at least 6 of the variables R are hydrogen

material
and the radical is water / alkyl, cycloalkyl, alkoxy or individual aromatic ring hydrocarbon radicals, with none of the substituents containing more than about 12 carbon atoms and the total number of carbon atoms in the substituents on the lactone ring not exceeding about 12. Unsubstituted ε-caprolactone, in which all the variables R stand for hydrogen, are derived from 6-hydroxy-hexanoic acid. Substituted £. -Caprolactones and their mixtures can be obtained by reacting an appropriately substituted cyclohexanone with an oxidizing agent such as peracetic acid (cf. US Pat. No. 3,064,008). The cyclohexanones can be prepared from substituted phenols or by other synthetic methods.

To the substituted ε-caprolactones, which according to the invention as Considered particularly useful include the various monoalkyl £. -caprolactones, such as monomethyl, monoethyl, Monopropyl, monoisopropyl, etc. to monododecyl-fc.-caprolactone; Dialkyl- ε-caprolactones, in which two alkyl groups on the same or different carbon atoms, but not

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both are substituted on the £ carbon atom; Trialkyl E-caprolactones, in which 2 or 3 carbon atoms of the lactone ring are substituted, as long as the £ carbon atom is not disubstituted j alkoxy £ -caprolactones, such as methoxy and Ethoxy £, caprolactone; and cycloalkyl, aryl and aralkyl caprolactones, such as cyclohexyl, phenyl and benzyl-έ-caprolactone.

It is also possible to use lactones with more than 6 carbon atoms in the ring, such as Γ-enantholactone and / η- caprylolactone.

The various lactones can be used individually or in combination. Should the lactone polyesters be used as intermediates for the reaction with diisocyanates in the production of Polyurethanes are used, usually mixtures Substituted and unsubstituted lactones are preferred to achieve optimal non-hardening properties.

Bifunctional initiators which can be used in the preparation of lactone polyesters with terminal hydroxyl groups include those organic compounds which contain 2 alcoholic hydroxyl groups, such as glycols of the formula H0 (CH ₂ ) _n OH, in which η has a value of 2 to 10 , Glycols of the formulas HO (CH ₂ CH ₂ O) _n H (Va) and H0 / CH (CH ^ CH ₂ o7 _n H (Vb), in which η has a value from 1 to 40, such as ethylene glycol, diethylene glycol, etc. ; 2,2-dimethyl-1,3-propanediol; 2,2-diethyl-1,3-propanediol; 3-methyl-1,3-pentanediol; methyl and ethyl diethanolamines; the various cyclohexanediols; 4,4'-methylenebiscyclohexanol ; 4,4'-isopropylidenebiscyclohexanol; the o-, m- and p-xylylene glycols; the hydroxymethyl-substituted phenethyl alcohols; the o-, m- and p-hydroxymethylpheny! Propanols; the various

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phenylene diethanols; the various heterocyclic diols, such as 1,4-piperazine diethanol etc. Furthermore, polyester polyols' suitable, the reaction of a dicarboxylic acid, its diester or dihalide with a molar excess of a diol, e.g. by reacting 1 mole of adipic acid with 2 moles of ethylene glycol, were manufactured.

Other suitable diols include polyoxyalkylated derivatives of difunctional compounds having two reactive hydrogen atoms. These difunctional compounds can contain primary or secondary hydroxyl groups, phenolic hydroxyl groups, primary or secondary amino groups, amide, hydrazino, guanido, ureido, mercapto, sulfino, sulfonamide or carboxyl groups. They are made by reacting diols of the class HO (CHp) _n OH, in which η has a value of 2 to 10, propylene glycol, thiodiethanol, xylene diols, 4,4'-methylenediphenol, 4,4'-isopropylidenediphenol and resorcinol; Mercapto alcohols such as mercaptoethanol; dibasic acids such as maleic, succinic, glutaric, adipic, pimeline, sebacic, phthalic, tetrahydrophthalic and hexahydrophthalic acids; Phosphoric acid; aliphatic, aromatic and cycloaliphatic primary monoamines, such as methylamine, ethylamine, propylamine, butylamine, aniline, cyclohexylamine; secondary diamines such as N, N ^f -dimethylethylenediamine; and amino alcohols with a secondary amino group, such as N-methylethanolamine, with alkylene oxides, such as ethylene oxide, propylene oxide, 1-butylene oxide. 2-butylene oxide, isobutylene oxide, butadiene monoxide, styrene oxide or mixtures of these monoepoxides are available.

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Suitable bifunctional initiators also include compounds which comprise a single alcoholic hydroxyl group and a primary or secondary amino group, such as the amino alcohols the general formula:

H0 (CH ₂ ) _n NH ₂ (VI)

in which η has a value from 2 to 10; other hydroxyalkylamines, such as N-methylethanolamine, isopropanolamine, N-methylisopropanolamine etc.; the aromatic amino alcohols, such as p-aminophenyl alcohol, p-amino-o (-methylbenzyl alcohol, etc .; the various cycloaliphatic amino alcohols such as 4-aminocyclohexanol, etc.

Among the bifunctional initiators, which are a total of two primary ones and / or contain secondary amino groups, include the aliphatic diamines of the general formula:

H ₂ N (CH ₂ ) _n NH ₂ (VII)

the monosecondary diamines of the general formula:

R »NH (CH ₂ ) _n NH ₂ (VIII)

and the disecondary diamines of the general formula:

R "NH (CH ₂ ) _n NHR" (IX)

in which η has a value from 2 to 10 and R "stands for alkyl, aryl, aralkyl or cycloalkyl; the aromatic diamines, such as m-phenylenediamine, p-phenylenediamine, toluene-2,4-diamine, toluene-2,6- diamine, 1,5-naphthalenediamine, 1,8-naphthalenediamine, m-xylylenediamine, p-xylylenediamine, benzidine, 3,3'-dimethyl-4,4 ^l -biphenyldiamine, 3,3'-dimethoxy-4 ', 4' -diphenyldiamine, 3,3'-dichloro-4,4 ^f -biphenyldiamine, 4,4'-methylenedianiline, 4,4'-

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Ethylenedianiline, 2,3,5,6-tetramethyl-p-phenylenediamine, 2,5-fluorenediamine and 2,7-fluoro diamine; the cycloaliphatic diamines, such as 1, ^ - cyclohexanediamine, 4,4'-methylenebiscyclohexylamine and 4,4'-isopropylidenebiscyclohexylamine; and the heterocyclic amines such as piperazine, 2,5-dimethylpiperazine and 1,4-bis (3-aminopropyl) piperazine.

As can be seen by the person skilled in the art, in the process according to the invention numerous other "known and customary" polyether and polyester diols with terminal hydroxyl groups are also used will.

_M (Chain Extender) The extenders "/ which are mixed with the above polyether or polyester diols are rapidly reacting bifunctional organic compounds from the group of diamines, amino alcohols and glycols with a higher reaction rate than the alkylene glycols or hindered amines. Such extenders include, for example Amino alcohols of the formula (VI) and the diamines of the formula (VIl). The glycols which can be used according to the invention have tertiary amine groups, a sulfur atom or a phosphorus group, such as ethylene glycol, diethylene glycol, thiodiglycol, bis (hydroxyethylhydroquinone) and N-methylethylene glycol, and phosphine oxides in general Formula:

0
R-PZTC _n H _2n ) 0H / ₂ (X)

in which η stands for an integer and R a hydrocarbon rest means, such as phenyl bis (hydroxyethyl) phosphine oxide.

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As long as at least one of the above extenders is used is, the reaction mixture can also one or more of the slower reacting extenders, such as an alkylene glycol or a hindered amine such as methylenebis (orthochloroaniline).

Usually diamines and amino alcohols are preferred because they provide branched polymers with high thermal stability. However, where this property is not of particular interest, the glycols described above can also be used with advantage will.

The extender selected for use in the process according to the invention or the extender mixture is in the polyether or polyester glycol soluble; if this is not the case, however, then a dispersant can be used for a practically uniform Distribution of the extender in the glycol can be used.

Any known conventional catalyst for the polyurethane reaction is added to the solution or dispersion of polyether and / or polyester and extender. Commonly, basic catalysts are used which are either inorganic bases such as sodium hydroxide or sodium acetate or, more commonly, tertiary amines and tertiary amine-forming materials. Triethylenediamine is advantageously used alone or together with other secondary catalysts. Other amine catalysts include N-methylmorpholine, triethylamine and N, N, N ¹ , N'-tetramethyl-1,3-diaminobutane. It can also be used non-volatile metal-containing catalysts, such as stannous octoate and dibutyl

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tin diacetate. As will be understood by those skilled in the art, various other catalysts can also be used.

The prepolymer is prepared by reacting one or more of the above polyethers and / or polyesters in a known manner with a sufficient amount of at least one organic diisocyanate to create a "quasi-prepolymer", ie a prepolymer in which the average ratio of isocyanate groups to Hydroxyl groups greater than about 2: 1. Suitable organic diisocyanates include ethylene diisocyanate, ethylidene diisocyanate, propylene diisocyanate, butylene diisocyanate, cyclopentylene-1,3-diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4 ^f -diphenylmethane diisocyanate, 2,2-diphenylpropane-4,4'- diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, xylylene diisocyanate, 1,4-naphthylene diisocyanate, 1,5-naphthylene diisocyanate, diphenyl 4,4 ^l -diisocyanate, azobenzene ^^ 'diisocyanate, dphenylsulfone-4,4'-diisocyanate , Dichlorohexamethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, furfurylidene diisocyanate, 1-chlorobenzene-2,4-diisocyanate, etc.

Particularly suitable for use in the process according to the invention is that in the application from the same date with the title "Polymerization catalysts for polyurethanes" (US application 351 "859 from April 17, 1973) described catalyst system, which hereby is included in the present application.

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In the above-mentioned US application, catalyst systems are described which consist of

(A) at least one basic amine catalyst for the polyurethane reaction with a catalytic effectiveness about the same or greater than trietylenediamine;

(b) at least one organometallic catalyst for the polyurethane reaction; and

(c) at least one basic amine catalyst for the polyurethane reaction with a catalytic activity below that of (a) and (b) catalysts present together in the catalyst system in an amount by weight about equal to or greater than the combined weight of catalysts (a) and (b) .. In particular wildly a catalyst (c) is used, the N ^ methyldicyclohexylamine, is an N-alkylmorpholine or tetramethylguanidine. For example, catalyst systems composed of 0.2 part of triethylenediamine, 0.2 part of alkyltin diacylate and 0.4 part of phenylmercuric propionate can be used per 100 parts of polymerization formulation, based on the reactants used will.

The polyurethane reaction mixture, consisting on the one hand of polyether and / or polyester diol, extender and diisocyanate catalyst and on the other hand consists of the prepolymer, m «n is obtained by combining the two groups of materials in one high-speed Mixing and injection molding equipment of a type currently available. A mixing and injection molding system has proven to be particularly useful from Desma, which is capable of mixing screw speeds of over 10,000 rev / nm.

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In the method according to the invention, a device with a supply and deformation system for the liquid polyurethane injection molding component can advantageously be used, as described in US application 352 076 of April 17, 1973 with the title "Method and device for the liquid injection molding of thermosetting
Mixtures with multiple components ".

The steps of introducing the liquid reaction mixture into the mold, curing the components of the mold, and removing them of the cured elastomer are known and customary.

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Claims (6)

Claims 1.- Process for liquid injection molding of polyurethane elastomers, characterized in that one (A) a solution or dispersion of at least one polyether and / or polyester diol with terminal hydroxyl groups, at least an organic bifunctional extender selected from the group of diamines, amino alcohols or glycols with a faster reaction rate than the alkylene glycols or hindered Amines and an effective amount of at least one catalyst for the polyurethane reaction with a prepolymer from the Reaction of at least one polyether and / or polyester diol with terminal hydroxyl groups with at least one organic Diisocyanate to create a prepolymer with an average ratio of free isocyanate groups to hydroxyl groups combined over about 2: 1, the rate at which the above components are combined to create a practically homogeneous liquid reaction mixture is sufficient, Ln which no noticeable polymerization before the introduction mixing into the mold is done; (b) introducing the liquid reaction mixture into the mold; . (c) the contents of the mold to create a molded polyurethane elastomeric article hardens and (d) removing the cured polyurethane elastomer article from the mold. 2.- The method according to claim 1, characterized in that the polyether and polyester diol each have a molecular weight of has around 2000. 409845/0972 3.- The method according to claim 1 and 2, characterized in that the extender is soluble in the polyether and / or polyester diol is. 4.- The method according to claim 1 to 3, characterized in that ethylene diamine or hydroxyethylamine is used as an extender will. 5.- The method according to claim 1 to 4, characterized in that thiodiglycol is used as the glycol. 6.- The method according to claim 1 to 5, characterized in that the components are mixed by a mixing screw, the rotates at a speed of about 10,000 revolutions per minute. The patent attorney: I " 409845/0972