CA2040055A1

CA2040055A1 - Process for the production of films for internally lining plastic molds and the use of the molds thus lined

Info

Publication number: CA2040055A1
Application number: CA002040055A
Authority: CA
Inventors: Joachim Wagner; Werner Rasshofer; Karl H. Dorner
Original assignee: Individual
Current assignee: Bayer AG
Priority date: 1990-04-13
Filing date: 1991-04-09
Publication date: 1991-10-14
Also published as: EP0451656A3; DE4012006A1; JPH068270A; EP0451656A2; KR910018454A

Abstract

Mo-3540 LeA 27,593 A PROCESS FOR THE PRODUCTION OF FILMS FOR INTERNALLY LINING
PLASTIC MOLDS AND THE USE OF THE MOLDS THUS LINED
ABSTRACT OF THE DISCLOSURE
The present invention is directed to a process for the production of films for internally lining molds for the production of film-clad plastic moldings by vacuum forming at temperatures above 20°C using quasi-thermoplastic films having a maximum thickness of 1 mm. The quasi-thermoplastic films used is based on a polyisocyanate polyadduct having a density of at least 0.6 g/cm3 which has been obtained by reaction of organic polyisocyanates, compounds having molecular weights of 1,800 to 12,000 which contain a statistical average of at least 2.5 isocyanate-reactive groups, and at least 5% by weight of one or more compounds selected from the group consisting of 1) diamines containing two primary and/or secondary aromatically bound amino groups and having molecular weights in the range from 108 to 400, 2) aliphatic polyols, which may contain ether groups and which have molecular weights of from 60 to 1799, 3) cycloaliphatic polyols, which may contain ether groups and which have molecular weights of from 60 to 1799, 4) aliphatic polyamines, which may contain ether groups and which have molecular weights of from 60 to 1799, 5) cycloaliphatic polyamines, which may contain ether groups and which have molecular weights in the range from 60 to 1,799 at an isocyanate index of 60 to 140 by reaction injection molding using closed sheet molds having a maximum height of 1 mm.

Mo-3540

Description

21)40~55 Mo-3540 LeA 27,593 A PROCESS FOR ~HE PRODUCTION OF FILMS FOR INTERNALLY LINING
PLASTIC MOL~S AND THE USE OF THE MOLDS ~HUS LINED
~ACKGROUND OF THE INVENTION
The present ~nvention relates to a new process for the production of films for internally lining molds for the production of film-clad plastic moldings by vacuum forming using films based on polyisocyanate polyadduots produced by reaction injection molding and to the use of the molds thus lined for the production of film-clad plastic moldings, and more par~icularly those based on f3amed polyisocyanate polyadducts.
The produc~don of quasi-thennoplastic polyisocyan~te polyadducts is already known (cf. for example German Offenlegungsschriften 3,733,756, 3,809,524 or 3,822,331).
According to these prior publications, moldings or films are prodl~ced from cross-linked quasi-therrnoplastic polyisoeyanate polyadducts using relatively high temperatures and excess pressure. The polyisocyanate polyadducts used may be present in various forms. 'rhus,the ~gh pressure forming of 4 ~ thick shee1s is also described in the Examples.
DESCRIPTION OF THE INVENU QN
It has now surprisingly been found that thin films having a maximum thickness of 1 mm and preferably From 0.3 to 0.8 mm, which are suitable for the internal lining of plastic molds by vacuum forming, can also be produced by reaction injection molding using starting materials of the type mentioned in the cited prior publications.
Accordingly, the present invention relates to a process for the production of films for internally lining molds for the production of film-clad plastic moldings by vacuum forming at temperatures above 20-C using quasi-thennoplas~cfilms having a maximum thickness of 1 mm, characterized in that the quasi-~ennoplas~cs films used are based on polyisocyanate Mo-3540 .. . .. ..

2 0~10 0~;5 polyadducts having a density of at least 0.6 g/cm3 which have been obtained by reaction of a) organic polyisocyanates, b~ compounds having moleoular weights of 1,800 to 12,000 which contain a statistical average of at least 2.5 isocyanate-reactive groups, and c) at least 5% by weight based upon the weight of component b) of one or more compounds selected from the group consisting of 1) diamines containing two primary and/or secondary aromatically bound amino groups and having molecular weights in the range from 108 ~o 400, 2) aliphatic polyols, which may contain ether groups and which have molecular weights of from 60 to 1799, 3) cycloaliphatic polyols, which may contain ether groups and which have molecular weights of from 60 to 1799, 4) aliphatic polyamines, which may contain ether groups and which have molecular weights of from 60 to 1799, 5) cycloaliphatic polyamines, which may contain ether groups and which have molecular weights in the range from 60 to 1,799 at an isocyanate index of 60 to 140 by reaction injection molding using closed sheet molds having a maximum height of 1 mm.
The present invention also relates to the use of the ;nternally film-lined molds for the production of film-clad plastic moldings.
The films to be used in the process according to the invention are films having a density of 0.6 to 1.4 and pre-ferably 0.8 to 1.2 g/cm3 and a maximum thickness of 1 mm and preferably 0.3 to 0.8 mm which have been produced by reaction Mo-3540 . . , ~ ~ ;

2~)~L0~15 injection molding from known starting materials using sheet molds of co~esponding d~nensions. In view of ~e fact ~at s~u~ng maten~s hav~g a func~ona~ty greater ~an hNo are ~so used for ~e manufacture of ~e pol~socyana~ po1yadducts ~ese ale cross-~nked pl~cs w~ch ~e "quasi-~ennopl~c".I~s1aner ~nnn~ atthe fiknsto be usedin ~eprocess accor~ng to theinvention may be ~ennopl ~ca~y moldedi.e.shaped under ~e influence of heat ~OUt p~sing through~mel~d s~ as ~ue ~ennoplas~c ma~n~s w~d.The"qu~i-~ennop1~c" ma~n~s do,infac~ not meltdunng ~e ~hennoplas~c moldings~p.
Substantially any of the organic polyisocyanates generally known and used in the art are suitable as component a3 for the production of the films. Suitable polyisocyanates include, for example, those having molecular weights above 137 and preferably from 168 to 290 and containing only aliphatically and/or cycloaliphatically bound isocyanate groups, such as for example 1,6-diisocyanatohexane, 1,2-diisocyanatododecane, 1,3-diisocyanatocyclobutane, 1,3- and 1,4-diisocyanatocyclohexane and mixtures of these isomers, l-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl cyclohexane (IPDI), ~,4- and/or 4,4'-diisocyanatod kyclohexyl methane or mixtures of these simple polyisocyanates. Other suitable polyisocyanates include urethane-, allophanate-, isocyanurate-, urea-, biuret- and/or uretdione-modified polyisocyanates based on aliphatic and/or cycloaliphatic polyisocyanates. Mixtures of unmod;fied diisocyanates with the modified polyisocyanates mentioned may also be used as component a). The polyisocya-nates containing aliphatically and/or cycloaliphatically bound isocyanate groups are often preferred because of the l~ght stability of the films produced from the~. If light stability is not a requirement, the usual aromatic polyisocyanates are eminently suitable as starting component a). Examples of such aromatic polyisocyanates ~nclude those having an NCO content of 10 to 59X by weightt such as for example 2,4-dilsocyanato-toluene, 2,6-diisocyanatotoluene, 1,2-bis-(4-isocyanatophenyl~-, .: -" ,. . .

.

- 3 a - 2C)~0055 ethane, alkyl-substituted and, more particularly, methyl-substituted diisocyanatodiphenyl methanes of the type described in European patents 24,6,65 or 46,556 and polyisocyanates of the diphenyl methane series and mixtures thereof. Mixtures of such polyisocyanates may also be used in the process according to the invention.
The polyisocyanates or polyisocyanate mixtures preferably used are those of the diphenyl methans series.

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.

4 204~55 Specific examples include 4,4'-diisocyanatodiphenyl methane, mixtures thereof with 2,4'- and, optionally, 2,2'-diisocya-natodiphenyl methane containing up to 70% by weight and preferably up to 20% by weight 2,4'-diisocyanatodiphenyl methane, based on the mixture as a whole, the content of 2,2'-diisocyanatodiphenyl methane generally not exceeding 5% by weight; polyisocyanate mixtures of the type obtained by phosgenation of aniline/formaldehyde condensates which, in addition to diisocyanatodiphenyl methane isomers of the type mentioned, may contain various quantities of higher homologous polyisocyanates (generally 5 to 60% by weight, based on the mixture as a whole); urethane-group-containing reaction products of such diisocyanates and/or polyisocyanates with less than stoichiometric quantities of aliphatic polyhydroxyl compounds having molecular weights in the range from 62 to 700, such as for example ethylene glycol, trimethylol propane, propylene glycol, dipropylene glycol or polypropylene glycols having a molecular weight in the range mentioned; and, diisocyanates and/or polyisocyanates modified by partial carbodiimidization of the isocyanate groups.
Component b) is selected from compounds containing isocyanate reactive groups and having molecular weights in the range from 1,800 to 12,000 and preferably in the range from 3,000 to 7,000 or from mixtures of such compounds. Component b~ must have an average functionality in the context of the isocyanate addition reaction of at least 2.5, preferably from 2.6 to 4.0 and more preferably from 2.8 to 3Ø Compounds particularly suitable as component b) are polyether polyols or mixtures of polyether polyols corresponding to these requirements, for example of the type disclosed in German Auslegeschrift ~, 622, 951 ( " the ' 951 reference"), column 6, line 65 to column 7, line 47. According to the invention, other preferred polyether polyols are those in which at least 50% and preferably at least 80% of the hydroxyl groups consist of primary hydroxyl groups. The hydroxyl polyesters, Mo-3540 ~0 4 0~)5 S

polythioethers, polyacetals, polycarbonates or polyester amides disclosed in the '951 reference are also suitable in principle as component b) according to the invention provided they comply with the requ;rements stated above. However, they are less preferred than the polyether polyols.
Other suitable starting components b~ include aminopolyethers or mixtures of aminopolyethers, ;.e., polyethers containing isocyanate-reactive groups of which at least 50 equivalent-% and preferably at least 80 equivalent-%
consist of primary and/or secondary aromatically or aliphatically bound, preferably aromatically bound, amino groups and, for the rest, of primary and/or secondary aliphatically bound hyroxyl groups. Suitable aminopolyethers of this type are, for example, the compounds described in European patent 081,701, column 4, line 26 to column 5, line 40. Polyesters containing amino groups which have molecular weights in the range mentioned above are also suitable, although less preferred, as starting component b~.
Mixtures of polyhydroxyl compounds with aminopolyethers may o~ course also be used as component b).
Component c) must comprise at least 5% by we;ght based upon the weight of component b) of one or more compounds selected from the group consisting of 1) diamines containing two primary and/or secondary aromatically bound amino groups and having molecular weights in the range from 108 to 400, 2) aliphat;c polyols, which may contain ether groups and which have molecular weights of from 60 to 1799, 3~ 3) cycloaliphatic polyols, which may contain ether groups and which have molecular weights of from 60 to 1799, 4) aliphatic polyamines, which may contain ether groups and which have molecular weights of from 60 to 1799, Mo-3540 : , ,: ~
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2~ 055 5) cycloaliphatic polyamines, which may contain ether groups and which have molecular weights in the range from 60 to :I,799.
Aromatic diamines of the type described in European patent OB1,701, column 5, line 58 to column 6, line 34 ("the '701 reference"), are eminently suitable as component c), with the diamines described as preferred diamines in the European patent also being preferred in accordance wi~h the present invention.
The polyols or polyamines which may be used as component c) may be selected from any non-aromatic compounds containing at least two isocyanato-reactive groups and having molecular weights in the range from 60 to 1,799, preferably in the range from 62 to 500 and more preferably in the range from 62 to 400. Suitable compounds of this type include, for example, polyhydric alcohols of the type disclosed in the '701 reference, column 9, lines 32 to 50. Other suitable compounds include, for example, aliphatic polyamines containing ether groups such as, for example, polypropylene oxides terminated by primary amino groups and having molecular weights in the range mentioned. Polyols containing cycloaliphatic rings, such as for example 1,4-dihydroxycyclohexane or 1,4-bis-hydroxymethyl cyclohexane, and polyamines, such as for example 1,4-cyclo-hexanediamine, isophoronediamine, bis-(4-aminocyclohexyl)-methane and bis-(3-methyl-4-aminocyclohexyl)-methane, are also suitable as component c).
It is a key feature of the process according to the invention that component c) be used in the production of films in such quantities that the percentage content by weight of 3C component c), based on the weight of component b), is at least 5% by weight and preferably at least 10% by ~eight. In a particularly preferred e~bodiment, the films are produced using (cyclo)aliphatic polyamines or polyols of the type mentioned under c) in such quantities that the molar ratio of Mo-3540 7 2~ (3~55 incorporated urea groups to incorporated urethane groups in the elastomers is at least 2:1.
Auxiliaries and additives may also be used in the production of films. These include, ~or example, internal mold release agents, catalysts for the polyisocyanate polyaddition reaction, blowing agents, surface-act;ve additives7 cell regulators, organ;c and inorganic pigments, dyes, UV and heat stabilizers, plast;cizers and fungistatic or bacteriostatic agents, for example of the type described by way of example in the '701 reference, column 6, line 40 to column 9, line 31.
The auxiliaries and additives optionally used also include fillers and/or reinforcing materials known Der se, such as for example barium sulfate, kieselguhr, whiting, m ka or, in particular, glass fibers. These fillers and/or reinforcing materials may be used in quantities of up to 80% by weight and are preferably used in quantities of up to 30% by weight, based on the total weight of the filled or reinforced ~ilms.
However, the films are preferably produced w;thout fillers and reinforcing materials.
The films are preferably produced by the one-shot process by mixing the polyisocyanate component a) with a mixture of the other components using suitable mixers and reacting the resulting mixture. Basically, the polyisocyanate polyaddition products may also be reacted by a ~Imodified Z5 one-shot process" in which the polyisocyanate component a) is reacted with part of component b) and, optionally, component c) to form NC0 semiprepolymers which are then reacted in one step with the mixture of the remaining components. Films may also be produced using the prepolymer principle, but always by 3~ reaction injection molding using closed sheet molds having the above-mentioned thickness. In every case, the NC0 index (number of NC0 groups divided by the number of NCD-reactive groups multiplied by 100) is from 60 to 140, preferably from 80 to 120 and more preferably from 95 to 115.

Mo-3540 . . .
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As mentioned above, component c) ~together with the amino groups, if any, present in component b)) is preferably gauged so that the molar ratio of urea groups to urethane groups in the elastomers is at least 2:1. In a particularly preferred embodiment, this ratio is at least 5:1. In practice, this means that component c) is an amine containing material and is preferably used in a quantity of 5 to 50% by weight and more preferably in a quantity of 10 to 40% by weight, based on the weight of component b).
If desired, the inner walls of the sheet molds may be coated with external release agents before the production of the films. The films are produced by otherwise exactly the same reaction inject;on molding (RIM) process descr;bed, for example, ;n 6erman Auslegeschrift 2,622,951, U.S. Patent 4,218,543 or the '701 reference.
If desired, the thickness of the films removed from the sheet molds may be further reduced by rolling at elevated temperature, for example at 150 to 190C, before further processing, although this is not generally necessary. The Films to be subjected to vacuum forming have a maximum thickness of 1.0 mm, preferably 0.1 to 1 mm and, more preferably, 0.3 to 0.8 mm.
"Yacuum formin3" in the context of the present ;nven-tion is understood to include any technique known per se in wh;ch the or;g;nal f;lm-like appearance of the polyisocyanate polyadduct used as starting material ;s changed under the effect of relatively high temperatures and vacuum. The process and associated apparatus are described, for example, by G. Gruenwald ;n "Thermoforming", Technom;c Publ. Co. Inc., Lancaster, Basle (1987).
The internal lining of the plastic molds by vacuum forming in accordance with the present invention takes place at temperatures of the films to be vacuum-formed above 20C, preferably in the range from 100 to 200C and more preferably in the range from 130 to 180DC, an absolute pressure, ;.e. a Mo-3540 , .. . .. .

g ~ 0 0 5 S
vasuum of 0.01 to 1,000 mbar and preferably 0.1 to 500 mbar, generally being applied during the vacuum form;ng step. Under these condltions, the molds can generally be internally linPd in 2 to 10 seconds. Since, the in-mold times required for the production of films by reaction injection molding are also very short, i.e. approx. 30 to 45 seconds, the process according to the invention represents a simple method - suitable for mass production - for internally lining plastic molds with high-quality film material.
~he films may be heated to the temperature required for vacuum forming, for example, by contactless heating with infrared lamps, by convection heating, by induction heating or by microwave irradiation.
The process according to the invention is suitable for the internal lining of any plastic molds of the type used in the production of plastic moldings. The molds lined in accordance with the invention may be filled with any plastics or any plastic-forming reaction mixtures. The molds pretreated in accordance with the invention are preferably used for the production of flexible to semirigid film/foam composites of polyisocyanate polyadducts containing urethane and/or urea groups, the foams generally having a density of 0.05 to 0.8 g/cm3. The production of foams such as these is known Der se and is described, for example, in "Kunststoff-Handbuch", Vol.
VII, edited by Vieweg and Hochtlen, Carl Hanser Verlag, Munchen (19~6) .
~he film-foam composites produced using the molds lined by the process according to the invention are suitable, for example, in the automotive industry as covers for instrument panels, swltch consoles, interior door trim, interior roof trim, center consoles, sun visors or, generally, for the production of seats, sofas or other soft seating, for the production of foam cushions, mattresses or for similar applications.

Mo-3540 ' :

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~ he invention is further illustrated but is not intended to be limited by the following examples in which all parts and percentages are by weight unless otherwise specified.
EXAMPLES
Example 1 (Preparation of a polyisocyanate polyadduct) The formulation shown below was processed as follows:
Machine: Laboratory piston metering unit Mold: Steel mold with internal dimensions of 300 x 200 x 3.5 mm, so that a 0.5 mm thick sheet or film is obtained.
Mixing head: MQ 8 (Hennecke, St. Augustin) Operating pressure: 180 bar Filling time: 1 second Raw material temperatures: 35C (A component), 30C (B component) Mold temperature: 50~C
In-mold time: 30 seconds.
Before production of the molding, the inner walls of the mold were coated with a commercially available external mold release agent ~RCTW, a product of Chemtrend).
A component:
Mixture of 70.5 parts by weight of a commercially available ~5 trifunctional aminopolyether, NH value 34, containing primary amino groups (~Jeffa~ine T
5000, a product of Texaco), 5.0 parts by weight of a commercially available trifunc-tional aminopolyether, NH value 387, containing primary amino groups (0Jeffamine T 403, a product of Texaco), 5.0 parts by weight Schwarzpaste N (a black pigment paste product of Bayer AG), 15.0 parts by weight 4,4'-diamino-3,3'-dimethyl dicyclo-hexyl methane, Mo-3540 . . . . - . ..

11 i;:~40~D5~
1.0 part by weight of a commercially ava;lable l~ght stabilizer (~Tinuvin 765, a product of Ciba-Geigy), 2.0 parts by weight phenyl di-(decylphenyl)-phosphite.
B component:
Semiprepolymer of 1-isocyanato-3,3,5-trimethyl-5-isocya-natomethyl cyclohexane and a polyether triol, OH Yalue 29, prepared by propoxylation of trimethylol propane. The NCO
semiprepolymer had an NCO content of 30%.
The components were mixed together in a ratio by weight of A to B of 100:32 (corresponding to an index of 110).
Mechanical data (after condition;ng for 1.5 hour at 130C) Density: 1.005 g/cm3 Tensile strength (DIN 53 504): 20 MPa Elongation at break (DIN 53 504): 160%
G'modulus (80CC) (DIN 53 445): 5 MPa E modulus in tension (RT)(DIN 53 457): 30 MPa Example 2 (process according to the invention3 The film produced in accordance with Example 1 was processed in a commercially available vacuum forming mach~ne (of the Formvac M type manufactured by Hydrochemie, ~urich).
A negat;ve mold of a box measuring 20 x 20 x 3 cm was used. The f;lm was heated for 55 seconds (approx. 160C) at a distance of 7 cm from the built-in IR lamp operating at maximum output and, immediately afterwards, was vacuum-formed by application of a vacuum of approx. 100 mbar. The box mold was satisfactorily lined in this way and may be filled, for example, with a reaction mixture reacting to form a polyurethane foam to produce a film-clad foam molding.
ExamPle 3 A film produced in accordance with Example 1 was again used in conjunction with a negative half-mold of an imitation of the bust of the Egyptian Queen Nefertiti (height 15 cm) which has deep and shallow depressions with sharply and gently curved edges and corners, which provides for Mo-3540 , 2040~)55 particularly good evaluation o~ the vacuum forming process.
Under the same conditions as in Example 2, a satisfactorily film-lined mold was again obtained.
Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be lim;ted by the claims.

Mo-3540 ~ $

Claims

1. In a process for the production of films for internally lining molds for the production of film-clad plastic moldings by vacuum forming at temperatures above 20°C using quasi-thermoplastic films having a maximum thickness of 1 mm, the improvement wherein the quasi-thermoplastic films used is based on a polyisocyanate polyadduct having a density of at least 0.6 g/cm which has been obtained by reaction of a) organic polyisocyanates, b) compounds having molecular weights of 1,800 to 12,000 which contain a statistical average of at least 2.5 isocyanate-reactive groups, and c) at least 5% by weight based upon the weight of component b) of one or more compounds selected from the group consisting of 1) diamines containing two primary and/or secondary aromatically bound amino groups and having molecular weights in the range from 108 to 400,

2) aliphatic polyols, which may contain ether groups and which have molecular weights of from 60 to 1799,

3) cycloaliphatic polyols, which may contain ether groups and which have molecular weights of from 60 to 1799,

4) aliphatic polyamines, which may contain ether groups and which have molecular weights of from 60 to 1799,

5) cycloaliphatic polyamines, which may contain ether groups and which have molecular weights in the range from 60 to 1,799 at an isocyanate index of 60 to 140 by reaction injection molding using closed sheet molds having a maximum height of 1 mm.

Mo-3540 2. The process of Claim 1, wherein the vacuum forming step is carried out at temperatures of 100 to 200C.
3. The process of Claim 1, wherein the film subjected to vacuum forming is heated by contactless heating before and/or during vacuum forming and the vacuum forming step is carried out by application of an absolute pressure of 0.01 to 1,000 mbar.

Mo-3540