DE2824003B2 - Process for the production of molded polyurethane articles - Google Patents

Description

A pressure roller that has softness as well as the ability to resemble natural rubber to its original shape regain while having much greater resilience against the solvents used in printing inks and of course, if possible, greater resistance to abrasion has long been the goal of roller manufacturers for the printing industry.

Because of their wear resistance and solvent resistance Polyurethanes appear to be suitable for the manufacture of printing rollers. Unfortunatelly it is Polyurethanes too strong to be used as a pressure roller without modification. The usual way to get them up to that Softening points where they are useful was the addition of plasticizers. This leads to how that As is known to those skilled in the art of plastics manufacture, a number of problems are immediately addressed. Around to get the required softness or suppleness (low hardness values or durometer values), it is necessary that substantial amounts of plasticizers be included in the composition. These are of relatively low molecular weight and in most cases are relatively soluble compounds. They have immediate effects on solvent resistance. In addition, the generated Softness the ability of the connection to return to its original shape when deformed (Elasticity) adversely affect. The plasticizer often migrates to and causes on the surface Wise efflorescence and of course leaves the underlying urethane harder. To make something soft in this way also adversely affects the wear properties. The ability to be a castable Producing soft, elastic polyurethane mass with high solvent resistance is thus considered to be a A desire to be fulfilled, especially for the printing industry, but also for other industries, the materials with similar properties would be an advantage.

The invention relates to the production of such compositions by introducing monovalent Fatty alcohols instead of some of the conventional plasticizers in conventional polyurethane casting compounds, which are currently used in the manufacture of printing rollers.

The US-PS 34 02148 describes the use of monovalent Fatty alcohols as chain terminators to produce urethane rubbers that are suitable for milling in conventional rubber compounding units for manufacturing vulcanizable urethane elastomers are suitable.

Although similar on the surface, the compositions of US Pat. No. 3,4 02,148 are in fact different from the invention. The well-known! The fifth compositions do not contain a curing or crosslinking agent to allow curing to a particular shape, but are intended for further rubber mixing and subsequent vulcanization or peroxide curing
Nor do they suggest the non-stoichiometric cure which the present invention has found to be at least preferred for optimal results.

The invention relates to the production of molded polyurethane articles through implementation

a) a polyurethane prepolymer with isocyanate end groups and a molecular weight of 400 to 10,000,
jo b) a polyol and

c) a phthalate or dibenzoate ester,

the polyurethane prepolymer being used in such an amount that the total isocyanate concentration is about 105% of the total concentration of hydroxyl groups (-100%), which is characterized in that a fatty alcohol having 5 to 26 carbon atoms is also reacted in such an amount that The proportion of hydroxyl groups in the total hydroxyl content of the system is 1 to 10% and that the ester component is used in an amount of less than 30% by weight of the uncured system
The compositions according to the invention can

Vi are cured to objects with durometer degrees of hardness from 15 to about 35 Shore A, the durometer hardnesses remain essentially constant with aging, so that compared to polyurethanes that have been plasticized with plasticizers alone,

V) have increased solvent resistance, so that they similarly have increased plasticizer bloom resistance and that it increased Have elasticity or elastic resilience. These hardened moldings are special

ν, useful for making pressure rollers.

The polyurethane moldings obtained according to the invention can be produced from known materials which are either commercially available or easily prepared by standard known methods. There

M) the polyurethane prepolymer with isocyanate end groups reacts with hydroxyl groups in other constituents of the hardenable mass, it becomes with these just before the Casting and hardening mixed. The other ingredients can be premixed, or they can be separated too

** · be added to the final mixture. Mixing, pouring and curing can then be done by conventional methods known to those skilled in the art.
The polyurethane prepolymers with isocyanate end groups

pen are compounds of a 1> ps which are known to the person skilled in the art familiar, you will be made up of essentially linear connections with two or more active hydrogen atoms, preferably exactly two active on average Hydrogen atoms that react with an isocyanate function and may form a urethane bond or an equivalent thereof, prepared these compounds are then reacted with a polyisocyanate to give the isocyanate-terminated polyurethane prepolymer. In principle, any organic polyisocyanate is suitable as long as it has isocyanate groups has only functional substituent groups that one Reaction with active hydrogen. Both alkylene and arylene diisocyanates are suitable examples of isocyanates are, without limitation, the following compounds:

a) alkane diisocyanates:

Ethylene diiscvanate, Trimethylene diocyanate, Propylene-li-diisocyanate, Tetramethylene diisocyanate, Butylene-13-diisocyanate Octadecamethylene diisocyanate;

b) alkene diisocyanates:

1-propylene-1,2-diisocyanate

2-propylene-1,2-diisocyanate, jo

1-butylene-1 i-diisocyanate, 3-butylene-1,2-diisocyanate, 1-butylene-13-diisocyana, 1-butylene-23-diisocyanate;

c) alkylidene diisocyanates:

Ethylidene diisocyanate Propylidene-1,1-diisocyanate, Propylidene-2,2-diisocyanate;

d) Cycloalkylene diisocyanates:

Cyclopentylene-13-diisocyanate, Cyclohexylene-13-diisocyanate, Cyclohexylene-1,2-diisocyanate, Cyclohexylene-1,4-diisocyanate;

e) Cycloalkylidene diisocyanates:

in

Cyclopentylidene diisocyanate cyclohexylidene diisocyanate;

f) carbocyclic aromatic diisocyanates:

m-phenylene diisocyanate, o-phenylene diisocyanate, p-phenylene diisocyanate, l-methyl-2,4-phenylene diisocyanate,

Naphthylene-1,4-diisocyanate, Diphenylene-4,4'-diisocyanate,

2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate,

Methylene bis (4-phenyl isocyanate), Xylylene-1,4-diisocyanate, Xylylene-1,3-diisocyanate,

^ '- Diphenylmetbanddiisocyanat, 4,4'-diphenylene propane diisocyanate;

g) Diisocyanates containing heteroatoms:

OCN-CH ₂ CH ₂ -O-CH ₂ Ch ₂ -NCO, 2,3-pyridine diisocyanate;

h) other diisocyanates.the various nonreactive.tive Substances contain:

l-chlorophenyl-2,4-diisocyanate,

13-dichlorophenyl-4,6-diisocyanate 1,4-dichlorophenyl-2 ^ diisocyanate l-chloro- ^ methoxyphenyl- ^ - dnsocyanate 1 -Methoxyphenyl-2,4-diisocyanate, l-MethyM-methoxyphenyl- ^ - diisocyanate

1-ethoxyphenyl-2,4-diisocyanate, 13-dimethoxyphenyl-4,6-diisocyanate !, 4-dimethoxypheny! -24-diisocyanate 1-Propoxyphenyl ^^ diisocyanate 1 -Isobutoxyphenyl-2,4-diisocyanate 1,4-diethoxyphenyl-2 ^ -diisocyanate;

i) other representative polyisocyanates:

Isophorone diisocyanate, Diphenyl ether 4,4'-diisocyanate

33'-dimethylbiphenyl-4,4'-diisocyanate 33'-dimethoxybiphenyl-4,4'-diisocyanate, 33'-dimethoxydiphenylmethane-4,4'-diisocyanate 33'-dichlorodiphenyldimethylmethane

4,4'-diisocyanate
Benzophenone 33'-diisocyanate, 3-butoxyhexamethylene diisocyanate, 1-4 -dimethylcyclohexane diisocyanate, 1-4 -dimethylnaphthalene diisocyanate, 1-4 -dimethylnaphthalene diisocyanate; Dicyclohexylmethane ^ '- diisocyanate Dicyclohexylmethylmethane ^^' - diisocyanate, dicyclohexyldimethylmethane-4,4'-diisocyanate, 2 ^ '- dimethyldicyclohexylmethane-4,4'-diisocyanate, 33 \ 5,5'-tetramethyidicyclohexyimethane-4,4'-diisocyanate

S-nitrotriphenylmethane ^^ '- diisocyanate, pyrene-Si-diisocyanate
Chrysene-2 ^ -diisocyanate,
Dianisidine diisocyanate,
Isopropylene-bis- [phenyl- or

cyclohexyl isocyanate],
Chlorodiphenyl diisocyanate,
4,4 ', 4 "-triphenylmethane triisocyanate, 1,33-triisocyanatobenzene and
Phenylethylene diisocyanate.

The compounds with active hydrogen contain hydrogen in the Zerewitinoff sense.

Suitable starting materials are the hydroxy compounds of the general formula HO — R — OH. where R is a divalent organic radical. The hydroxyl groups can be of any one for the Urethane reaction with isocyanate groups may be of a suitable type, such as alcoholic or phenolic Hydroxyl groups. The following dihydroxy compounds are examples of compounds useful as reactants in the invention.

a) alkynediols with a chain length of 2 to 20 carbon atoms, such as

2,2-dimethyl-1 ^ -propanediol,

Ethylene glycol, Tetramethylene glycol, Hexamethylene glycol, Heptamethylene glycol, Decomethylene glycol;

b) alkeniols, such as

l-propylene-l ^ -diol,

2-propylene-1,3-diol,

1-ButyIen-l ^ -dioI,

3-butylene-1,2-diol,

1-hexylene-U-dJol,

l-BatyIen-23-diol;

c) Cycloalkylenediols, such as

Cyclopentylene-l ^ -diol,
Cyciohexylen-li-diol,
Cyclohexylene-lß-diol,
Cyclohexylene-1,4-diol;

d) carbocyclic aromatic diols, such as

Cetechol,

Resorcinol,

Quinol,

1 -MeÄyl ^ 't-benzenediol,

2-methyl-1 ß-naphthalenediol,

3,4-toluene diol,

Xylylene-1,4-diol, Xylylene-U-diol,

1,5-naphthalene dimethanoI,

2-ethyl-1-phenyl-3-butene-1,3-diol, 2 £ -di (4-hydroxyphenyl) propane;

e) Diols containing heteroatoms, such as

Di (/? - hydroxyethyl) ether,
e-methyl ^ -pyrimidinediol,

HO-CH ₂ -CNH ( _{CH 2) 4} NHCCH ₂ -OH

15th

20th

25th

30th

35

45

Bis (/ miydroxyethyl) formal,
Dithiodiglycol.

Among the polyfunctional polyols which are suitable as reactants according to the invention, there are also polyalkylene ether glycols of the general formula HO— (RX) n — H, where R is identical or different alkylene radicals with up to about 19 carbon atoms, X is an oxygen atom and m means a sufficiently large number so that the molecular weight of the polyalkylene ether glycol is from 400 to 10,000. The polyalkylene ether glycols within this general formula, such as polyethylene glycols, polypropylene glycols, polybutylene glycols, polytetramethylene glycols, polyhexamethylene glycols, polyhexamethylene glycols, or the like, which are catalyzed by the corresponding monomers of glycols, condensation and the corresponding monomers of the glycols Condensation of low molecular weight alkylene oxides, such as ethylene oxide, propylene oxide and the like, either with themselves or with glycols, such as ethylene glycol, propylene glycol or the like, are preferred.

Polyalkylene arylene & therglycols derived from those described above Polyalkylene glycols differ in that that they arylene radicals such as phenylenes or naphthylene or either unsubstituted or substituted, such as by alkyl or aryl groups and the like may contain substituted arylene radicals in place of some of the alkylene radicals of the polyalkylene glycols can also be used as a polyol reaction partner. Polyalkylenearylene glycols are common for this The type used for the purpose usually contain at least one alkylene ether radical having a molecular weight of about 500 per arylene radical present

Essentially linear polyesters containing multiple isocyanate-reactive hydroxyl groups are one another preferred class of reactive organic polyfunctional Polyols used in making polyurethanes useful in the invention be, can. While the production of polyesters that are suitable for this purpose, according to the prior art described in great detail and does not constitute a part of the present invention per se, the explanation can be found here it should be mentioned that polyesters of this type by condensation of a polyhydric alcohol, generally of a saturated aliphatic diol, such as ethylene glycol, propanediol (U), propanediol (1,3), butanediol-0.3), Butanediol- {1,4), pentanedioHU), pentanediol-0,5), HexandioKU), HexandioKl.ö), diethylene glycol, Dipropylene glycol, triethylene glycol, tetraethylene glycol and the like, as well as a mixture of such diols with one another and in minor amounts of polyols with more than two hydroxyl groups, preferably saturated aliphatic polyols such as glycerine, Trimethylolethane, trimethylolpropane, pentaerythritol, Sorbitol and the like, with a polycarboxylic acid or an anhydride thereof, generally a dicarboxylic acid or an anhydride thereof which is either saturated or only benzoid unsaturation contains, such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, Azelaic acid, sebacic acid, malic acid, phthalic acid, cyclohexanedicarboxylic acid, and endomethylenetetrahydrophthalic acid or the like, as well as their isomers, homologues and other substituted derivatives, such as chlorine derivatives, or with mixtures of such acids with one another and with unsaturated dicarboxylic acids or anhydrides thereof, such as maleic acid, fumaric acid, citraconic acid and itaconic acid and the like, as well as with polycarboxylic acids with three or more carboxyl groups, such as aconitic acid and the like, can be produced.

The substantially linear polyesters commonly used in making polyurethane resins preferably have molecular weights in the range of about 750 to about 3000. In addition, they generally have relatively low acid numbers, such as acid numbers not significantly above about 60 and preferably as low as practical can be, such as ? Or less. Accordingly, they generally have relatively high hydroxyl numbers, such as from about 30 to 700. In making these polyesters, an excess of polyol over polycarboxylic acid is generally used to ensure that the substantially linear polyester chains contain a sufficient amount / amount of reactive hydroxyl groups .

Nitrogen-containing polyfunctional polyols can also be used as polyol reactants.

Among such materials are the polyester amides conventionally used in the manufacture of Polyurethane resins are used, d. H. those with molecular weights ranging from about 750 to about 3000, with acid numbers ranging from about 60 to a minimum, such as 2 or less, and with hydroxyl numbers in the range from about 30 to 700, and also high molecular weight polyamino alcohols, such as hydroxy propylated alkylenediamines of the general formula

(HOH ₆ Cj) ₂ NR _n -N (C ₃ H ₆ OH) ₂

10

where R. denotes an alkylene radical having 2 to 6 carbon atoms, of which N, N ,, N ' ₁ N'-tetra- (2-hydroxypropyl) -ethylenediamine is a representative example, as well as higher analogs of the same, such as hydroxypropylated polyalkylene polyamines of the general formula

(HOH ₆ Cj) ₂ NR ₁₁ -NR ₀ -N (CH ₆ OH) ₂ > n CH ₆ OH

wherein R _{1 is} as defined above (see US Pat. No. 2,697,118).

As can be easily seen, mixture of the various above-described reactive organic polyfunctional polyols also for the production or at used in the production of polyurethane prepolymers which are useful according to the invention.

It can be seen that polyols which have been reacted with isocyanates by known methods, in the Molecular weight range from 400 to 10,000, usually from 600 to 7,000, suitable polyurethane prepolymers are mers with isocyanate end groups for the process according to the invention.

Poly (ethylene adipate) polyester with a molecular weight of about 1300, which have been reacted with toluene diisocyanate, turned out to be particularly useful preferred in practicing the invention.

The polyols used as the polyurethane prepolymer curing agents of the invention are in the art known It is obvious that the above-mentioned polyols are suitable for this. Branched chain connec- 4; fertilizers are also suitable and can be preferred in many cases. Examples of these are compounds, such as pentaerythritol, trimethylolpropane and triethoxytrimethylolpropane. It is of course to be noted that in many cases an acceleration of the speed the curing action between isocyanates and polyhydroxy compounds up to practical values the use of cure rate catalysts requires use where appropriate Conventional curing catalysts are well within the skill of those of ordinary skill in the art and does not form part of the invention. The term "polyol as a polyurethane prepolymer curing agent" includes also the combination with such a catalyst, which can be carried out at will by the person skilled in the art of the invention is to be selected

The term "fatty alcohol" with 5 to 26 carbon atoms means the linear saturated monovalent ones Alcohols in that area. Examples of these are as follows:

n-amyl alcohol,
n-hexyl alcohol,

Tridecyl alcohol, Myristyl alcohol, Stearyl alcohol, Behenyl alcohol, Crotyl alcohol,

n-octyl alcohol,

n-decyl alcohol,

Lauryl alcohol, Cetyl alcohol, Arachidyl alcohol and Lignoceryl alcohol

The linear saturated monohydric alcohols can be used singly or in combination with each other will.

The phthalate ester or dibenzoate ester plasticizers named for the invention are those conventionally used be used for the purpose of making soft urethane castings. Examples of the same are dimethoxyethylphthalal, propylene glycol dibenzoate and dipropylene glycol dibenzoate, which are known as Proven beneficial for use in polyester-based polyurethane prepolymers and their analogues. Dioctyl phthalate is suitable for use in polyether based polyurethane prepolymers and their analogs particularly suitable.

The curable compositions according to the invention can, if desired, by combining the various components are made before casting and hardening.

The polyurethane prepolymer normally makes up 50 to 75 percent of the total composition, but is in each case its proportion so that the ratio of NCO / OH in the mixed composition before the hardening is about 105%. The saturated fatty alcohol is used in such amounts that its Share of the total hydroxyl content of the system in the range from 1 to 10%, preferably in the range from 3 up to 5%

The ester plasticizers themselves are used in proportions of less than 30% of the uncured system, usually used in the range from 25 to 28%. The fatty alcohol concentration must be in proportion to any free hydroxyl groups that may be present in a particular plasticizer will.

To get durometer hardnesses close to 20 Shore A through the use of plasticizers alone, one usually has to disregard about 39 to 43% of these plasticizers in the composition of hardeners and fillers that can be used.

The polyol curing agent is incorporated in a sufficient amount to provide the required 105% NCO / OH ratio above the hydroxyl functions supplied by the plasticizer and the fatty alcohol to surrender. Of course, this ratio of 105% does not have to be exact, but can be from about 102 to about 110% can be varied, with 105% are preferred

It is sometimes convenient to premix the plasticizer and fatty alcohol so that it is a standard amount the mixture can be used in the preparation of any batch of the curable composition, without a setting in the system for variations in the free hydroxyl content of special plasticizer batches is required

One skilled in the art will find that usually

Fillers used to reduce costs, to absorb printing ink or as reinforcing agents are useful, can also be incorporated into the compositions according to the invention. The selection special fillers or other conventional additives and their proportions within the knowledge of the average specialist.

The following examples are provided for further explanation the invention.

example 1

Diisopropanol dibenzoate and dimethoxyethyl phthalate were mixed with n-octadecanol or decanol in the in Table I mixed proportions shown. The relevant analytical values for the compounds and the mixtures are shown in Table II.

Table I. link

mixture

Amount (parts by weight)

12 3 4

Dimethoxyethyl phthalate
Dipropylene glycol dibenzoate
Decanol
n-octadecanol

Tibelle II

- 970 970

969 946 - -

31 - 30 -

- 54 - 53

Compound or mixture

Hydro-acid% xyl number number H ₂ O

Dipropylene glycol dibenzoate 0 0, (X, 0.14 Dimethoxyethyl phthalate 0.4 0.08 033 Decanol 350.0 0.04 0.69 n-octadecanol 198.0 0.25 0.37 Mixture 1 9.02 0.03 0.13 Mixture 2 12.68 0.03 0.28 Mixture 3 13.50 0.06 033 Mixture 4 14.42 0.08 0.25

A poly (ethylene adipate) with hydroxyl end groups and a molecular weight of about 1300, which with Toluene diisocyanate had been converted to a prepolymer with terminal isocyanate groups, with the mentioned plasticizer-fatty alcohol mixtures and Tnäthoxvtrimethylolpropane in the in Mixtures shown in Table III. The total stoichiometric ratio of NCO / OH was 105% in each case. The mixtures were then cured for 2 hours at 149 ° C and 16 Baked in for hours at 100 ° C. The Shore A hardness and the appearance on the days after cure are also listed in Table III

Table III Amount (parts by weight) Prepolymer 100 100 100 100

Mixture 1 40

Mixture 2 40

Mixture 3 40

Mixture 4 40

Triethoxytrimethy- 93 9.5 9.5 9.5

lolpropane

Days hardness (Shore A) / appearance

after

Hardening

30 / clear

30 / clear

32 / clear

32 / clear

33

33

33

33

33

33

33

33

29 / clear

29 / clear

30 / clear

30 / clear

29 / clear

29 / clear

29 / clear

30 / clear

30th

30th

30th

30th

30th

30th

30th

30th

30 / clear

30 / kiar

30 / clear

30 / clear

31

31

31

31

31

31

31

31

Example 2

In an analogous procedure to Example 1 were further mixtures of the above mixture produced. The proportions and results are given in the table IV.

Table IV

material

Amount (parts by weight) Prepolymer

Dimethoxyethyl phthalate

Mixture 1

Mixture 2

Mixture 3

Mixture 4

Triethoxytrimethylolpropane

100
50

100 100 100 100

45

45

9.5 9.5 9.5 9.5

Days
after
Hardening

Hardness (Shore A)

1 35 28 25th 22nd 18th 2 35 28 25th 22nd 18th 3 35 28 25th 22nd 18th 6th 35 28 25th 22nd 18th 7th 35 28 25th 22nd 18th 8th 35 28 25th 22nd 18th 27 35 28 25th 22nd 18th 34 35 28 25th 22nd 18th 41 35 28 25th 22nd 18th 48 35 28 25th 22nd 18th 55 35 28 25th 22nd 18th 57 35 28 25th 22nd 18th

Example 3

Using a method analogous to that of Example 1, a polyester with hydroxyl end groups [poly (ethylene adipate)] with a molecular weight of about 1300 and with toluene diisocyanate end groups up to

bo an NCO percentage of 4.40 (65 parts), a mixture of dirnethoxyphthalate (933%) and 1-octadecano! (6.1%) (29.4 parts) and triethoxytrinethylolpropane (6.0 parts) mixed together and added using conventional casting and curing techniques Cast standard pressure rollers. After curing, the rollers showed a durometer hardness of 25 Shore A. After grinding, the durometer hardness was 26 Shore A.

Claims (1)

Claim: Process for the production of polyurethane moldings by reaction a) a polyurethane prepolymer with isocyanate end groups and a molecular weight of 400 to 10,000, b) a polyol and c) a phthalate or dibenzoate ester, the polyurethane prepolymer being used in an amount such that the total isocyanate concentration is about 105% of the total concentration of hydroxyl groups, characterized in that that you also have a fatty alcohol with 5 to 26 carbon atoms in such an amount converts that its proportion of hydroxyl groups in the total hydroxyl content of the system makes up 1 to 10% and that the ester component is used in an amount of less than 30% by weight of the uncured system used