DE1570468C3 - Use of a fully cross-linked polyurethane as a self-adhesive adhesive - Google Patents

Description

The invention relates to the subject of the patent claims. The reference »Angewandte Chemie«, 1947, page 257 ff, is an early basic summary regarding the then time relatively new reaction of isocyanates with polyols for the production of polyurethanes. So also does this reference not address the creation of fully crosslinked polyurethanes suitable for the Manufacture of adhesives are suitable. It is described there that when using 3- and higher-valent alcohols of medium to higher molecular weight are completely crosslinked and infusible Receives crowds. Such infusible masses are not provided according to the invention but rather rather sticky masses that are useful for the manufacture of pressure-sensitive self-adhesive Adhesives.

The same also applies to US-PS 31 14 735 and 30 12 993. The process of these patents manufactured products are solids. Accordingly, in the first-mentioned patent specification is a Use of the products for the manufacture of machines or engines, diaphragms and valve closures etc. and in the second mentioned patent the use for the manufacture of products as specified for tires and tubes. That such products are not suitable for the production of Self-adhesive adhesives are obvious.

The process for producing the fully crosslinked polyurethanes is therefore that one or several polyols with at least three hydroxyl groups per molecule with or without one or more diols .and / or one or more monools with the stoichiometric amount of an organic polyisocyanate be implemented, the hydroxyl-containing compounds in sufficient amount depending on of their molecular weights to be a fully crosslinked reaction product with the To form polyisocyanate, which has an average chain length between 130 and 285 chain atoms.

Under stoichiometric amount of an organic 6 ^r> polyisocyanate that amount is meant in this polyisocyanate required to react with all the hydroxyl groups of the polyols, diols, and mono-ols, to form product is a fully cross-linked reaction.

The term »chain length« in the sense used here is the length of a chain expressed in chain atoms, and measured from a branch point to the adjacent branch a side chain from the first-mentioned chain or measured from the branch point of the first chain mentioned to the end of the first mentioned. Chain if there is no branch at one end wears, understood.

The term "ketteriatom" only refers to the atoms in the main chain and does not include them Side chain atoms.

Preferably, the reagents are in a flowable state on a substrate such as paper or tissue or a thin plastic sheet where they react to form a pressure-sensitive adhesive.

The expression "self-adhesive (pressure-sensitive) adhesive" in the sense used here denotes a mass that ^{remains tacky over a wide temperature range, namely at at least -20 to 70 0} C and adheres to most surfaces when at the temperature of the environment in the absence of Heat. Humidity or other means a low pressure is applied.

The polyols used according to the invention can be hexols, e.g. B. sorbitol, pentols, e.g. B. Arabitol. Tetrols, e.g. B. pentaerythritol or triols, such as. B. glycerin. Also copolymers of these polyols with Propylene oxide and / or ethylene oxide can be used instead of the unmodified polyols. Examples of diols that can be used are poly (ethylene glycol) and poly (propylene glycol). Examples of usable Monools are ethylene glycol monomethyl ether and n-butanol.

Various combinations of hydroxyl containing compounds; H. Monools, diols, triplets, etc. can be used in the invention, e.g. a single type of tetrol or triol, mixtures different tetrols and / or triols with different molecular weights, mixtures of one or several types of diols and mixtures of one or more types of tetrol and / or triol and one or several types of monool. It is, however, regardless of which combination of hydroxyl-containing Compounds used, essential that such amounts are used that when reacted with an organic polyisocyanate, the mean chain length of the reaction product between 130 and 285 Chain atoms. For example, if a single triol of the glycerol-propylene oxide copolymer type is used, it should have a molecular weight between about 4,000 and 8,000 when used with a low molecular weight polyisocyanate is implemented. The range can be lower when it comes to one high molecular weight polyisocyanate is implemented.

The mean chain length of the reaction product, expressed as the number of atoms in the chain ending with a certain polyol and a certain polyisocyanate is formed according to the following Procedure determined. For example, a copolymer of glycerine and propylene oxide will be with one Molecular weight of 5000 reacted with the stoichiometric amount of 4,4'-diisocyanatodiphenylmethane. The mean total atomic weight of each arm of the

Triols is called, d. H. Adopted in 1666. Of each

Arm of the triol is believed to be composed of propylene oxide units

(-CH (CHa) -CH ₂ -O-)

and each unit has a total atomic weight of 58 which is believed to be only three Atoms, namely the chain atoms —C — C — O— is equivalent to. The number of chain atoms in each arm of a triol unit of the reaction product is therefore

1666 x ^, ie 86. The 4,4'-diisocyanatodiphenylmethane units in the reaction product have the formula
-CO-NH-C ₆ H ₄ -CH ₂ -C ₆ H ₄ -NH-CO

for which the number of chain atoms is assumed to be 11 (whereby three chain atoms are assumed _{for each —C 6} H _{4 group).} Therefore the chain length of the reaction product is on average 86 + 11 + 86, ie 183 chain atoms. Conversely, this method can be used to determine which polyol / polyisocyanate mixtures will produce a reaction product which has an average chain length between 130 and 285 chain atoms.

When one or more triols or one or more diols are reacted with an organic polyisocyanate it is found that self-adhesive adhesives are formed with more consistent properties, when the triols have low molecular weights, e.g. B. 1000 to 3000.

If a mixture containing at least one triol and at least one diol is used, so can Proportions which theoretically make a poorly self-adhesive adhesive, i.e. H. one too hard in practice result in a reaction product which shows good properties as a self-adhesive adhesive. This is on attributed to the occurrence of a change in the chain lengths of the reaction product. So can a high proportion of chain lengths with an average of 130 to 285 chain atoms are generated from mixtures, the proportions of which would not be expected to make a good pressure-sensitive adhesive, though the reaction product obtained would be ideal. By "ideal" is meant that the length of all chains of the Reaction product is the same.

The organic polyisocyanate used in the invention can be aliphatic or aromatic, e.g.

4,4'-diisocyanatodiphenyimethane,

Toluene diisocyanate,

Hexamethylene diisocyanate,

Triphenyl methane triisocyanate,

2,4,4'-triisocyanatodiphenyl ether and

Polymethylene polyphenyl isocyanate.

Usually an accelerator such as dibutyltin dilaurate or tin 2-octoate is added to the reaction mixture added to hardening.

If necessary, an antioxidant can also be added to the reaction mixture before hardening or gelling be incorporated. This stabilizes the adhesive against loss of tack on exposure the air.

The self-adhesive adhesives used according to the invention have the advantage that they are not in one Solvents or dispersants must be dissolved or dispersed in order to be applied to a substrate to become and that the degree of stickiness and non-transferability of the mass to a large extent Temperature range, namely from -20 to + 120 ° C not changes significantly.

The following examples are intended to illustrate the invention.

example 1

This example uses portions of 10 g each of different triols with different molecular weights individually with 4,4'-diisocyanatodiphenylmethane in the presence of 0.1 g of dibutyltin dilaurate as an accelerator mixed and it is shown that only those triols, the molecular weights in the calculated Range for the formation of reaction products with average chain lengths between 130 and 285 chain atoms have, are suitable. The amount of diisocyanate used in each case was calculated stoichiometric amount for the reaction with all hydroxyl groups present. more details result from Table I, in which the following abbreviations have been used for simplification:

50

55

60

MG = MG Molecular weight of the tnol. DDM = 300 Amount of 4,4'-diisocyanatodiphenylme- 3000 thans in g. RPCL = 4000 mean total atomic weight of each ket 5000 length of the reaction product. CLA = 6000 Number of atoms in each chain length of the 9000 Reaction product. Table I. DDM RPCL - CLA A. 12.75 450 2J B. 1.28 2250 114 C. 0.953 2916 149 D. 0.75 3582 183 E. 0.625 4250 218 F. 0.425 6250 325

The triols used in this example were all commercially available and were all copolymers of glycerine and propylene oxide, with the exception of the triol with a molecular weight of 9000, which is a terpolymer of glycerine and propylene oxide with an ethylene oxide unit at the end of each Arm of the triplet.

The RPCL and CLA values were calculated using the method described above, using the total atomic weight of the propylene oxide units in each arm of the 9,000 molecular weight triol as 3000 minus the total atomic weight of a triolethylene oxide unit

(-CH ₂ -CH ₂ -OH)

i.e. 3000-45 = 2955, and the number of chain atoms due to the two ethylene oxide units of the reaction product

(-CH ₂ -CH ₂ -O-)

with 6, d. H. two units per chain was assumed.

Mixtures A through F were then cured. Mixture A cured in a few at room temperature Minutes. Mixture B cured slowly at room temperature, but in one hour at 70 ° C. the Mixtures C through E cured at 70 ° C for one and a half hours. Mixture F cured in two hours at 70 ° C.

The properties of the crosslinked reaction products obtained are shown in Table II:

Table II

A = hard, brittle - firm.

B = not sticky, rubber-like solid.

C = slightly softer and stickier than B.

D = soft, non-transferable, somewhat sticky, semi-solid (adhesive value = 217g).

E = soft, non-transferable, sticky, semi-solid (adhesive value = 45 g).

F = very soft, transferable, very sticky, semi-solid.

From this it follows that of the mixtures A to F only the mixtures C, D and E are for use are suitable as pressure sensitive adhesives.

The adhesive values of mixtures D and E were measured at room temperature with a Dunlop tackmeter (British Patent 7 41 214) measured.

Example 2

This example shows the production and properties of a pressure sensitive adhesive that made from a mixture of triplets of different molecular weights.

A mixture of 10 g of a triol of molecular weight 4000, 10 g of a triol of molecular weight 5000, 20 g of a triol of molecular weight 6000, 2.99 g of 4,4'-diisocyanatodiphenylmethane and 0.3 g of dibutyltin dilaurate was about V / 2 hours at Hardened at 70 ^{° C.} The resulting crosslinked reaction product was quite hard, showing no signs of transferability at 100 ° C, and had an adhesive value of 516 g.

Example 3

This example shows the production and properties of a pressure sensitive adhesive that was made from a mixture containing a triol and a diol.

4 Mixtures G through J were made using various triols and diols as shown in Table III in which all parts represent parts by weight.

In Table III, the following abbreviations have been used for the sake of simplicity:

5000T

300T

1500D

2000D

DDM
DZD

Table III

2000D - 2.0 - 11.5 5 DDM 1.2 1.0 3.1 2.7 DZD .. 0.1 0.1 0.1 0.1

Each of the mixtures G to J was cured IV2 hours at 70 ⁰ C to form a somewhat soft sticky reaction product. The adhesive values for the reaction products of mixtures G to] were 600 g, 580 g, 550 g and 770 g, respectively. Mixtures I and J were found to give reaction products that were less sticky but more consistent in batch properties than Mixtures G and H. None of the reaction products showed any signs of transferability at 100 ^° C.

Example 4

This example shows the production and properties of a pressure sensitive adhesive that was made from a mixture of a triol and a monool.

4 Mixtures K through N were made as shown in Table IV in which all parts are parts by weight manufactured.

In Table IV, the following abbreviations have been used for the sake of simplicity:

Copolymer of glycerine and propylene

lenoxide with a molecular weight of 5000.

Copolymer of glycerine and propylene

lenoxide with a molecular weight of 300.

Molecular weight poly (propylene glycol)

1500.

Molecular weight poly (propylene glycol)

2000.

4,4'-diisocyanatodiphenyl methane.

Dibutyltin dilaurate.

6000T, 5000T = K Copolymers of Glycerin and : III. N and 4000T 10 Propylene oxide with molecular weight _ - th of 6000.5000 and 4000 respectively. M. - = - Methyl oxytol. _ 10 MO 0.005 - 0.020 DDM = 0.64 as with table 10 0.97 and DZD 0.1 0.010 0.1 Table IV L. 0.96 0.1 6000T 10 5000T - 4000T 0.028 MO 0.80 DDM 0.1 DZD

5000T

300T

1500D

10

2.5

11th

The mixtures K to N were at 80 ° C for 1 hour cured for a long time and the properties of the reaction products obtained are shown in Table V.

Table V

K = quite hard, not transferable, adhesive value 380 g. L = fairly soft, poorly transferable, adhesive value 385 g.

M = quite hard, not transferable, adhesive value 463 g. N = quite hard, not transferable, adhesive value 480 g.

The bond values given in this description were measured at room temperature using a Dunlop tackmeter (British Patent 7 41 214).

Claims (2)

Patent claims: 1. Use of a fully crosslinked polyurethane with an average chain length of 130 to 285 Chain atoms obtained by reacting a) one or more polyols with at least three hydroxyl groups optionally with one or more diols and / or one or more per molecule Monools with b) the stoichiometric amount of an organic polyisocyanate has been produced, optionally with the addition of an antioxidant as a self-adhesive adhesive. 2. Use according to claim 1, wherein the polyurethane is obtained by reacting a) a copolymer from glycerine and propylene oxide, as a triol, optionally with polypropylene glycol as a diol, and / or ethylene glycol monomethyl ether prepared as a monool with b) 4,4'-diisocyanatodiphenylmethane has been.