DE3220097C2 - Use of a reactive mixture as a curable adhesive - Google Patents

Abstract

The invention relates to a curable adhesive which is to be prepared from the components by mixing them before use and which contains a polyol and a polyisocyanate and / or its prepolymer as active ingredients. The polyol is a reaction product of an aryl or aralkyl polyol having a molecular weight of 100 to 400 with an oxirane of the general formula (formula) in which R ↑ 3 is a hydrogen radical or an optionally halogenated hydrocarbon group with 1 to 4 carbon atoms or the group -CH ↓ 2OR ↑ 4, in which R ↑ 4 denotes an alkyl or alkenyl group, and where within the polymeric molecule the group R ↑ 3 is the same or different, with an average of 1 to 5 mol of the oxirane being added on per hydroxyl group of the polyol. The isocyanates known from the prior art are used as isocyanates. Polyol and polyisocyanate are present in such a ratio that 0.95 to 1.25 isocyanate groups of the polyisocyanate correspond to one hydroxyl group of the polyol. The adhesive properties of the adhesive are retained even under the influence of moisture or water; at the same time, the adhesives adhere well to plastic surfaces.

Description

wherein R ^{3 is} a hydrogen radical, an optionally halogenated hydrocarbon group with 1 to 4 ¹⁵ carbon atoms or the group -CH ₃ OR ⁴ , in which R ^{4 is} an alkyl or alkenyl group,

where within the polymeric molecule the groups R ^{3 are} identical or different, and on average

1 to 5 mol of the oxirane have been added per hydroxyl group of the polyol,
B) a polyisocyanate and / or its prepolymers! in an amount that a hydroxyl group des

Polyol correspond to 0.95 to 1.25 isocyanate groups of the polyisocyanate, and optionally
²⁰ C) include additives such as accelerators, adhesive auxiliaries, pigments and / or fillers

as a curable adhesive.

ΐ \ Curable adhesives based on reaction products of polyetherols or polyesterols with poly-

} -f cyanates or polyisocyanate polymers are known and z. B. In the Kunststoff-Handbuch, Volume VII,

I "Polyurethane", Vleweg-Höchtlen, Carl Hanser Verlag, Munich, 1965, p. 719 ff., Described. Will poly-

V, 30 etherole used as a polyol component, a disadvantage of this adhesive is their poor adhesion to plastic

Ij fabric surface.

j | Reaction products of Po, ^and / esterolen namely polyisocyanates or their prepolymers adhere better to

??, plastic surfaces, but their adhesive properties deteriorate under the influence of moisture or

il water.

if 35 The invention is based on the object of providing curable two-component adhesives based on a polyol and

Ψ_ to improve a polyisocyanate or its prepolymers so that the good jaw properties also under

> j. Influence of moisture or water are retained, but at the same time good adhesion to plastic

§ Surfaces are achieved or maintained. The curing temperature and the curing speed of the polyol

§ Isocyanate adhesive should not be influenced as much as possible.

?.: 40 This task is solved by using a reactive mixture

j | j A) a reaction product of an aryl or aralkyl polyol with a molecular weight of 100 to 400,

, f-. except for a novolak, with an oxirane of the general formula

V ^{45 rJ}

t CH ₂ -CH

% 5 « ⁰

wherein R ³ is a hydrogen radical, an optionally haiogenierte hydrocarbon group having 1 to 4 ^carbon; Substance atoms or the group -CH ₂ OR ⁴ 1st, in which R ⁴ denotes an alkyl or alkenyl group, the groups R ^{3 being the} same or different inside the polymeric molecule, and on average 1 to 5 mol of the oxirane per hydroxyl group of the polyol have been deposited
⁵⁵ B) a polyisocyanate and / or its prepolymer In an amount that a hydroxyl group of the polyol

0.95 to 1.25 isocyanate groups of the polyisocyanate, and optionally
; C) customary additives, such as accelerators, adhesive auxiliaries, pigments and / or fillers

as a curable adhesive.

^Wl A preferred adhesive is characterized in that it contains as polyol is the reaction product of a ■ V. Compound of the general formula R ¹ ^ Rj _n -OH) _n , where R ^{1 is} a radical derived from benzene, naphthalene or anthracene, R ^{2 is} a divalent aliphatic hydrocarbon radical with 1 to 4 carbon atoms, ;; = 0 or I, / n = 2 or 3, with an oxirane containing. The divalent radical R allphatlsche hydrocarbon ² may be a methylene, ethylene, propylene or butylene radical, said propylene and butylene or branched may be ^65th

'' ■: If the index «= 0, it is aryl polyols; If the index n = 1, it is an aralkyl polyol.

Examples of compounds of the general formula I.

r '- (r;, - oh) "

are. "Resorcinol, pyrogallol, phloroglucinol, 1,4-Bls- (hydroxymethyl) benzoI, hydroquinone, 2,7-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 1,8-dihydroxynaphthalene, 2,6-dihydroxyanthracene.
As polyols, the adhesives can also be the reaction product of a compound of the general formula

Z—

where Z is a ^ -little stliphatic hydrocarbon radical with 1 to 6 carbon atoms,

P = 1 or 2,

'4 = 2 or 3 and

R ^: and

η have the meaning already given,

with an oxirane included.

The radical Z is a ^ -lesser allphatic hydrocarbon radical with 1 to 6 carbon atoms, z. B. the rest

CH ₃

- CH ₂ - or - C - or

CH ₃

-CH-CH ₂ -

Examples of polyols of the general formula II which are reacted with an oxirane in the KJebmittel are, are: 2,2-Bls- (4-hydroxyphenyl) -propane, bis- (4-hydroxyphenyl) -methane, l, l, 2-tris- (4-hydroxyphenyO-ethane, 1,3-tris- (4-hydroxyphenyl) -propane, bis- (2-hydroxyphenyl) -ethane or 2,2-bis- (4-hydroxymethylphenyl) -propane.

Also suitable as polyols which are present in the curable adhesives when reacted with an oxirane are Compounds of the phenyl type of the general formula

(R ² -OH)

In this formula, the radical R ² , as already described for formula I, denotes a divalent aliphatic hydrocarbon radical with 1! Hs 4 carbon atoms. The index η is 0 or 1, the index ρ is 1 or 2. Examples of suitable compounds are: 2,2'-dihydroxybiphenyl, 4,4'-dihydroxybiphenyl, 2,2 ', 4'-trihydroxybiphenyl, 2,2'- Bls- (hydroxymethyl) biphenyl.

The aromatic rings contained in formulas I to III can additionally have 1 to 4 carbon atoms containing alkyl groups. Examples of such compounds are: Methylphloroglucin, 2,5,6-Trlmethylresorcln, 4-ethyl-5,6-dimethyl-resorcinol, 4-propyl-2,7-dlhydroxy-nap; ithaline or 4,6-DI-tert.-butylpyrocaterine.

Particularly favorable results with regard to the adhesion of the adhesive to plastic surfaces and with regard to the behavior towards the action of moisture and water show the adhesives when they are used as Polyol contain the reaction product of an aryl or aralkyl polyol with 1.5 to 3 mol of an oxirane.

Compounds of the general formula can be used as oxiranes

R ³

CH ₂ -CH

IV

be used.

The group R ¹ can be a hydrogen radical. The oxirane is then ethylene oxide. The group R ¹ can be an alkyl group having 1 to 4 carbon atoms. R is preferred ^! an alkyl group having from 1 to 4, especially 1 b's 2, carbon atoms. If R ^{3 is} a methyl group, it is propylene oxide. The alkyl group may optionally be halogenated and e.g. B. have chlorine residues. An example of such a halogenated group R ^J is the CH ₂ CI and the CH ₂ CCl ₃ groups. The alkyl group can also be unsaturated.

An example of such an unsaturated alkyl group is the vinyl or allyl group.

The group R ^J can also have the meaning of the group -CHj-OR ⁴ , where R ^{4 is} an alkyl or alkenyl group. An example of a suitable alkyl group is the butyl group; An example of a suitable alkenyl group is the vinyl or allyl group.

As oxiranes, in addition to the already mentioned ethylene oxide and propylene oxide z. B. the following connections the following are used: butylene oxide; Isobutylene oxide; Eplchlorohydrin; Eplbromhydrln; Trifluoromethylethylene oxide; 1,2-chloro-3,4-epoxybutane; I, I -Dlchlor-2,3-epoxybutane; 1,1,1-trichloro-3,4-epoxybutane; Methyl glycldyl ether; Ethyl glycldyl ether; Isopropyl glycldyl ether; ten-butyl glycidyl ether; n-hexyl glycldyl ether; Ethylhexyl glycldyl ether; Phenyl glycldyl ether; Chloφhenylglycldylether: Nltrophenylglycidylether; Vinyl glycidyl ether; Allyl glycldyl ether, butadiene monoxide.

Within the polymeric molecule, the meaning of the group R ¹ can be the same or different. Propylene oxide is preferably used as the oxirane.

The catalysts known from the prior art, in particular basic catalysts, such as. B. Sodium methylate, sodium hydroxide, potassium hydroxide or calcium hydroxide, but also acidic catalysts, such as. B. Bortrifluorld etherate used.

Up to 85% by weight of the polyol obtained by reacting an aryl or aralkyl polyol with an oxirane can be replaced by other polyhydroxy compounds. Such polyhydroxy compounds are dl or polyfunctional allphatlsche Polyalkylenoxldderlvate, as z. B. obtained by adding oxiranes to aliphatic alcohols with at least two hydroxyl groups. There can also be those known per se Polyesterols as well as castor oil can be used. You can also use low molecular weight polyacrylate polymers or -Use copolymers with at least two hydroxyl groups. These additives make it possible to modify the properties of the adhesive in the desired catfish and to use them z. B. to make it more flexible or yours To lower viscosity.

The polyisocyanates known from the prior art can be used quite generally as polyisocyanates. Polyisocyanates with the following formula are preferred

NCO

NCO

where η is 2 3, or

CH ₂

NCO

CH ₂

OCN- (CH _2), - NHCO- N - CONH- (CHj) ₆ -NCO

(CHJ ₆
NCO

CH ₂ O-CONHR-NCO
CH ₁ -CH ₁ -, (- CH _! 0-C0 _N "R'- _N C0
CH ₂ O-CONHR ³ -NCO

CH ₃ CH ₃

where R is the remainder

and or

means

These isocyanates are commercially available. However, other polyisocyanates, such as. B. 1,6-hexamethylene diisocyanate; 2,4,4-trlmethyl-1,6-hexamethylene di-cyanate; S-isocyanatomethyl O ^ S -trlmethylcyclohexyiisocyanate; ], 4-tetramethylene terminal isocyanate; 2,4- and 2,6-hexahydrotylene diisocyanate; Hexahydro-5,3 resp. -M-phenylene diisocyanate; 1,3- and 1,4-phenylene diisocyanate; 2,4- and 2,6-toluene diisocyanate; 4,4'-DHsocyanatodiphenylmethane; Naphthylene-1,5-diisocyanate; m-xylylene diisocyanate; Tris- (4-! Socyanatopheny!) -Thiophosphal; 4,4 ', 4 "-trilsocyanatotriphenyl methane; 2,4,6-triisocyanatotulol or 2,4,4'-triisocyanatodiphenyl ether, suitable

net. However, the isocyanates must meet the condition that they have at least two isocyanate groups on average have per molecule.

As prepolymers of the isocyanates, their partial reaction products with polyether or polymer polyols can be used a molecular weight - 2000 can be used, the polyether or polyester polyols Im average molecule have at least two hydroxyl groups and wherein the polyisocyanates with These polyols are reacted in such a ratio that 1.5 to 3 isocyanate groups of a hydroxyl group; n correspond.

Examples of suitable polyether oils are linear or branched polyether oils based on ethylene oxide, Propylene oxide and butylene oxide, polythioethers and adducts of ethylene oxides with polyamines and alkoxylates Phosphoric acids.

Examples of suitable polyesterols are linear or branched polyesterols, as they are made from polyvalent, preferably dibasic carboxylic acids, such as adipic acid, sebacic acid, phthalic acid, halogenated phthalic acids, Maleic acid, benzene !, 2,4-tricarboxylic acid, monomeric, lower or lower fatty acids and polyvalent ones Alcohols such as B. ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycols, 1,3-butanedol and -1,4, 2,2-dimethylpropandlol-1,3, hexanedol-1,6, 1,1,1-trimethylolpropane, hexanetrolene or glycerine on UbIt- '5 chem ways can be obtained.

The reaction of the polyisocyanates with the polyether or polyester polyols thus takes place in such Ratio that there are on average at least two isocyanate groups per molecule in the reaction product.

The Aushärtungszelt or Aushärtungstenveratur of the adhesive may in known catfish essential ^m Hch by the addition of an accelerator shortened or be reduced. A block is therefore particularly preferred which contains up to 2% by weight, based on the sum of the polyols and polyisocyanates, of a tertiary amine and / or an organotin compound as an accelerator. Particularly tertiary amines are dimethylbenzylamine, dicyelohexylmethylamine, dimethylphenol, dimethylamineethanol, 1,2-dimethylimidazole, N-methyl- or N-ethyl-morpholn, dimethylcyc'.ohexylamine, l-aza-blcyclo- (3,3,0) octane or 1,4-diazablocyclo- (2,2,2) -octane are suitable. Examples of useful organotin compounds are dibutyltin dllaurate or tinndD-octoate.

Pigments and / or fillers can also be added to the adhesive as auxiliary materials. Both inorganic and organic products, such as. B. titanium oxide, elsenic oxide, chromium oxide, barium sulfate, quartz mer \ Talc, calcium carbonate, Neuburg Siliceous Earth, Betonlt, suitable.

The adhesives cure at room temperature or at a moderately elevated temperature. As the adhesive are liquid. It is not necessary to use a solvent. However, it is desirable that the Preparation is very low viscosity, inert solvents, such as. B. lower ketones, ethers, esters or aromatic solvents can be used.

The adhesives are easy to process because the polyol component they contain is liquid. Implementation with the polyisocyanates takes place at room temperature and can be accelerated by heating. the Adhesion of the adhesive is on a wide variety of substrates, such as plastic surfaces, metals, wood, silicate Surfaces, good. The adhesive properties are also improved when exposed to water or moisture not or only insignificantly influenced.

The adhesives are to be used with advantage in particular when the adhesive joints are particularly good Influence of water should have no or only a slight drop in peel strength.

In the following examples the adhesives are compared with regard to their composition and their properties explained in more detail. All quantitative data in the examples relate to parts by weight.

Production of the polyols to be used as component A in the reactive mixture

50 g of pyrogallol are dissolved in 140 g of propylene oxide, 0.42 g of potassium methylate are added and the mixture is heated to a temperature of 125 ° C. in an autoclave over the course of 1.5 hours. The temperature is maintained until almost all of the propylene oxide has accumulated and the pressure in the reaction vessel has fallen again. This is _g

the case after about 3 hours. After cooling, small amounts of unreacted propylene- ⁵⁰ S are drawn off

oxide in vacuo at 80 ° C, neutralized with hydrochloric acid and separates off the salt formed. The dried, The polyol obtained in almost 100% yield has a hydroxyl number of 365 mg KOH / g and an average value Molecular weight of 465, determined by measurement in a vapor pressure osmometer. The polyol thus contains im Average 2 moles of propylene oxide attached per mole of hydroxyl group of the pyrogallol. The viscosity of the polyol is 7000 mPa ■ s at 25 ° C.

In a similar way, other polyhydroxyl compounds (= starting polyols) and propylene oxide are made or other oxiranes further polyols, which are described in Table 1. The Reaction with the oxiranes in suitable inert solvents, such as. B. ethylene glycol methyl ether or dioxane.

Manufacture of the adhesive and testing of the adhesive properties
a) Manufacture of adhesives from polyols and polyisocyanates

To produce the adhesive, the polyols are mixed with one another ^{with various polyisocyanates in the specified 6:> mixing ratio.} The polyols are usually used in solvent-free form. If the adhesive requires low processing viscosities, inert solvents such as esters, ketones or aromatics can be used as thinners.

Four commercially available products are used as polyisocyanates, under the designation b, a polyphenyl-polymethylene-polyisocyanate (Raw MDI) of the general formula

NCO

NCO

CH

J 0.7

and under the name b _2, a triisocyanate of the formula
b ₂ OCN- (CH ₂ ) S -NHCO-N -CONH- (CH ₂ J ₆ -NCO

(CHj) ₆

NCO

Both polyisocyanates are used in a solvent-free form. The name b ₃ is a polyisocyanate of the formula

CH ₂ O-CONHR ⁵ -NCO
CH ₃ -CH ₂ - C - CH ₂ O-CONHR ⁵ -NCO

CH ₂ O-CONHR ⁵ -NCO

where R is the remainder

CH ₃

and or

means.

used, which is present as a 75% by weight solution in ethyl acetate.

Further, under the designation b ₄ a 60 wt .-% solution in methyl ethyl ketone of a reaction product of 3 MoI 2,4-Toluylendlisocyanat and 1 mol of a polyester trlfunktlonellen oils having a molecular weight of 600, obtained from adipic acid, ethylene glycol, 2,2- Dimethylpropanediol-1,3 and Trlmelhylolpropane, used.

The content of free isocyanate groups, based on the solids, is:

Polyisocyanate b, 31.2 wt. "

Polyisocyanate b ₂ 22.7 wt. "

Polyisocyanate b ₃ 13.0% by weight

Polyisocyanate b ₄ 11.2 wt .- *

Other additives, such as accelerators, bonding agents, pigments and fillers, can be dissolved or pearled These additives are expediently added to the polyol prior to mixing with the polyisocyanate admits.

The exact recipes of the adhesive are shown in Table 2. The recipes No. 1 to II describe the reactive mixtures to be used as adhesives. Then follow under the recipes No. 12 to No. 13 comparative adhesive.

The comparative adhesive no. 12 contains a difunctional instead of the polyamide to be used according to the invention Polyetherol based on propylene and ethylene oxide with a hydroxyl number of 90 mg KOH / g.

Comparative adhesive no. 13 contains a polyeslerol instead of the polyols to be used according to the invention with a functionality of approx. 2.5 and a hydroxyl number of 109 mg KOH / g. The polyester is through Condensation of adipic acid with diethylene glycol, ethylene glycol and trimethylol propane has been obtained.

b) Testing the adhesive properties

The drum peel strength test according to DIN is used to test the adhesive tape from a technical point of view S3 295 used. The drum peeling strength is determined on two different compounds:

Composite aluminum / polyethylene (PE) Composite aluminum / epoxy resin-glass fiber laminate (GRP)

The aluminum sheets are made of the quality Al Cu Mg 2p! and are degreased and subjected to a chromate-sulfuric acid pickling process (Picklirig pickling). The polyethylene is roughened and pretreated, and the epoxy resin-glass fiber laminate (GRP) is sanded.

The adhesive used in an amount of 80g / m ^J solids applied to the adherend and the solvents, if any, at room temperature or elevated temperature, for example. B. 70 ° C, evaporates. The adhesive is cured at 90 ° C. for 20 minutes under a pressure of 0.5 N / mm ^J. After cooling, it is peeled at 20 ° C.

The aluminum / GRP test specimens are also stored in hot water at 95 ° C for three days carried out. Before the peel test, the test specimens are cooled in water at 20 ° C and are still moist peeled off. This hot water storage is very well suited as a Kura time test to determine the resistance of the adhesive! to be checked against water and moisture.

The strength values obtained are listed in Table 3. The values show that the Comparative adhesive No. 12, which contains a polyetherol, provides low strengths because it does not adhere well. Of the Comparative adhesive No. 13 based on polyesterol adheres better to polyethylene and fiberglass laminate, but it falls however, the strength decreases in the hot water test.

In Fig. 1 Is the dependency of the drum peeling strength de? Composite aluminum / polyethylene from the The amount of propylene oxide attached to 2,2-Bls- (4-hydroxyphenyl) propane is shown. As a polyisocyanate component the polyisocyanate b was used. One recognizes that high strengths are only possible in a narrow one Area of attached Propylenoxld can be obtained.

Tabel ! - polyols

Polyol formulation

Starting polyol

added molar amount of oxirane OH-Zah! Viscosity 25 ° C
per MoI OH starting polyol polyol polyol (mPas)

Component A of the reactive mixture to be used according to the invention

1 Pyrogallol 2.0 propylene oxide Polyetherol
Polyesterol 2 Phloroglucine 1.7 propylene oxide 3 1,4-bis (hydroxymethyl) benzene 1.5 propylene oxide 4th 2,2-bis (4-hydroxyphenyl) propane 1.5 propylene oxide 5 Bis (4-hydroxyphenyl) methane 1.5 propylene oxide 6th 2,7-dihydroxynaphthalene 1.7 propylene oxide 7th 2,2'-dihydroxybiphenyl 1.6 propylene oxide 8th 1,4-bis (hydroxymethyl) benzene 2.0 ethylene oxide 9 2,2-bis (4-hydroxyphenyl) propane 0.8 ethylene oxide + 1.0 propylene oxide 10 2,2'-dihydroxybiphenyl 1.9 propylene oxide 11th 2,2-bis (4-hyaroxyphenyl) propane 1.5 propylene oxide Polyol component of comparative adhesives 12th
13th -

365 7000 415 84000 357 220 284 80000 295 50000 316 14000 304 17000 300 200 283 60000 280 11000 284 80000 90 3000 109 4000

Table 2 - Adhesive Formulations

Recipe no.

Polyol parts by weight

Polyisocyanate parts by weight

Molar ratio OH: NCO

Other approaches parts by weight

1 100 96 b, 1: 1.1 - 2 100 119 b, 1: 1.2 - 3 100 102 b, 1: 1.2 20 titanium dioxide 4th 100 78 b, 1: 1.15 - 5 100 102 b ₂ 1: 1.05 0.02 dibutyltin dilaurate 6th 100 94 b, 1: 1.1 15 MW propylene glycol 7th 100 88 b, 1: 1.2 - 8th 100 86 b, 1: L2 - 9 100 163 b ₃ 1: 1.0 - 10 100 187 b ₄ 1: 1.0 - 11th 100 128 b, 1: 1.2 100 castor oil + 200 Cslciurncarbcr.at 12th 100 26 b, 1: 1.2 - 13th 100 31 b. 1: 1.2 -

Table 3 - Application testing of the adhesives

Sticky Drum peel strength DIN 53 295 Al / GRP 5 3 Al / GRP middle Nmm / mm 145 39 after 3 days of hot water recipe
XTv Al / PE For this 1 sheet storage No. 70 62 68 60 1 302 65 61 2 295 67 62 3 285 59 55 4th 288 68 61 5 265 63 57 6th 291 60 55 7th 287 51 45 8th 275 49 42 9 250 57 54 10 240 Comparative adhesives U 305 12th 2 13th 15th drawings

Claims (1)

Claim:
Use of a reactive mixture ^ς A) a reaction product of an aryl or aralkyl polyol with a molecular weight of 100 to 400, with the exception of a novolak, with an oxirane of the general formula R ^{3 10} CH ₂ -CH