FI91081B - Solvent - free, polyurethane - based hot melt adhesive mixture and method for its preparation - Google Patents

Description

91081

Solvent-free, polyurethane-based hot melt adhesive mixture and method for its preparation

Polyurethane bases for the manufacture of polyurethane adhesives for the manufacture of polyurethane

The present invention relates to "hot-melt" reactive urethane-based hot melt adhesive compositions having a low viscosity and improved cohesion and adhesion strength by adding low molecular weight acrylic resins to the compositions. According to one embodiment of the invention, the acrylic monomer (s) is polymerized in the non-isocyanate component of the polyurethane prepolymer, after which the prepolymer is reacted with suitable isocyanate groups to form a hot melt adhesive blend with

Hot melt adhesives are 100% solid materials that do not contain or require any solvents. They are solid materials at room temperature which, however, melt when heated to a liquid or fluid state, in which form they are applied to the surface of the substrate. As it cools, the adhesive becomes solid again and its cohesive strength is restored. Hot melt adhesives differ in this respect from other types of adhesives which are obtained in solid form by removing or evaporating the solvent present therein or by polymerizing them.

To obtain the desired physical properties, most hot melt adhesives are formed from thermoplastic (thermoplastic) materials that are used as a melt at high temperatures and that bind quickly upon cooling. Unfortunately, their 2 thermoplastic nature also results in a bond that is sensitive to heat, and which bond may break even when exposed to moderate heat.

Hot melt adhesive compositions which are applied as a melt, which solidify on cooling and which then cure as a result of a chemical crosslinking reaction, have been prepared using special thermosetting materials such as polyurethanes. These hot melt adhesives have good heat resistance, but have little inherent strength and resemble a thick ointment or grease before crosslinking. In addition, these polyurethane-based hotmelt adhesives do not sufficiently adhere to many commercial substrates, such as polyvinyl chloride film, Mylar, or aluminum. Attempts have been made to improve the initial adhesive strength of polyurethane-based hot melt adhesives by adding certain thermoplastic resins, for example, in accordance with U.S. Patent 3,931,007, issued January 6, 1976 to Uchigaki et al. However, these thermoplastic resins are generally high molecular weight materials (i.e., greater than about 100,000), so their addition greatly increases the coating viscosity of the adhesive, which in turn requires the addition of plasticizers or tackifiers to reduce the viscosity sufficiently to facilitate adhesive application. Although the addition of these plasticizers and tackifiers reduces the hot viscosity of the formed adhesive, the relatively large amounts required adversely affect the adhesion properties of the polyurethane-based hot melt adhesive, especially as the bond ages.

Accordingly, it is an object of the present invention to provide an improved polyurethane-based hot melt adhesive composition characterized by better initial adhesion to an unusually wide variety of substrates, as well as heat resistance even after aging of the bonds.

91081 3

The features of the invention are defined in the appended claims.

In the context of the invention, it has been found that the addition of urethane precursor polymers to low molecular weight polymers formed from ethylenically unsaturated active hydrogen-free monomers provides hot melt adhesives which are solid at room temperature and can be easily coated at a viscosity of 120,000 to 50,000. At C without the need to add other adhesion promoters or plasticizers. These adhesives have good initial cohesive strength and good strength after aging of the cured bond. In addition, the use of these adhesives provides improved properties on a wide variety of substrates, including difficult-to-bond substrates such as polyvinyl chloride, Mylar (DuPont polyester film), and ai umi i ni.

The low molecular weight polymer may be added to the polyol prior to reaction with the isocyanate components, or may be added to the preformed prepolymer. The products of the invention can also be formed by simultaneously polymerizing the urethane prepolymer and the ethylenically unsaturated monomers. The polyurethane polymer can also be polymerized in ethylenically unsaturated monomers, which are then polymerized to a product of the invention. Alternatively, ethylenically unsaturated monomers can be polymerized in a polyol using free radical polymerization. In this embodiment, the isocyanate components are then polymerized with the resulting mixture using conventional condensation methods for polymerization. The advantage of this latter polymerization process is that the molecular weight (defined as intrinsic viscosity) of the resulting vinyl polymer can be excellently controlled, and this process further yields a polymer that does not contain interfering impurities. In addition, the simplification of handling, the reduction of the materials required and the avoidance of temporary packaging and storage will significantly reduce costs.

Detailed Description of the Preferred Embodiments

Any ethylenically unsaturated monomer which can be polymerized by free radicals and which does not contain active hydrogen can be used in the invention. The invention most commonly uses C 1 -C 18 esters of acrylic and methacrylic acids, such as, but not limited to, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, n-propyl or isopropyl acrylate, and the like methacrylates. Mixtures of compatible (meth) acrylate monomers can also be used. Such mixtures, including mixtures of butyl and methyl methacrylate, are well known in the art. Other ethylenically unsaturated monomers such as vinyl esters (e.g. vinyl acetate and vinyl propionate), vinyl ethers, fumarates, maleates, styrene, acrylonitrile, ethylene, vinyl ethers, etc. can also be used, as well as copolymers thereof. The choice of the particular monomer (s) will largely depend on the desired end use of the adhesive. For example, it will be apparent to one skilled in the art that certain monomers provide a pressure sensitive adhesive, while other monomers produce a pressure insensitive material. Likewise, the monomers can be suitably selected to form structural adhesives, conductive adhesives, and the like.

Urethane prepolymers are compounds traditionally used in the art for the preparation of hot melt adhesive compositions based on polyurethane. In general, the prepolymer is prepared by polymerizing a polyisocyanate with a polyol by a condensation-based method, preferably by polymerizing a diisocyanate with a diol. Useful polyols are, for example,

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91081 5 polyhydroxyethers (substituted or unsubstituted polyalkylene ether glycols or polyhydroxy-polyalkylene ethers), polyhydroxy-polyesters, adducts between polyols and ethylene or propylene oxide and monosubstituted esters of glycerol.

Any suitable organic polyisocyanate can be used in the invention, for example, ethylene diisocyanate, ethylidene diisocyanate, propylene diisocyanate, butylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, 1,3-cyclopentylene, cyclopentylene -1,4-diisocyanate, cyclohexylene-1,2-diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,2-diphenylpropane-4,4'-diisocyanate, p-phenylene di - isocyanate, m-phenylenediisocyanate, xylylene diisocyanate, 1,4-naphthylenediisocyanate, 1,5-naphthylenediisocyanate, diphenyl 4,4'-diisocyanate, azobenzene-4,4'-di isocyanate, diphenylsulfone-4,4'-diisocyanate, dichlorohexamethylene diisocyanate, furfurylidene diisocyanate, 1-chlorobenzene-2,4-diisocyanate, 4,4 ', 4 "triisocyanate triphenylmethane, 1,3,5-triisocyanato-benzene, 2,4,6-triisocyanato-toluene, 4,4'-dimethyldiphenyl lymethane-2, 2 ', 5, 5-tetraisocyanate, and the like.

The proportions of polyisocyanate and polyol components to be combined are selected so that the resulting urethane prepolymer is characterized by an isocyanate content of about 0.25-15%, preferably about 10%. In addition, the ratio of isocyanate equivalents to hydroxyl equivalents (known as the isocyanate index) should be greater than 1, but not more than about 2. Keeping the isocyanate index low reduces the free isocyanate content in the final hot melt adhesive mixture to less than about 4%, preferably less than 1 %. It should be noted that higher concentrations of free isocyanate present adversely affect the melt formulation as they result in the release of toxic fumes when the adhesive is heated to the application temperature. Higher amounts of free isocyanate may also lower the viscosity of the adhesive and reduce its initial bond strength. The exact amount of polyisocyanate in the polymerization depends on the equivalent weight of the polyol, the amount of polyol, and the particular polyisocyanate used. In general, the amount of polyisocyanate required to achieve the desired isocyanate concentration ranges from about 5 to 55% of the final prepolymer.

Within the broadest scope of the invention, the ethylenically unsaturated monomer can be polymerized to a relatively low molecular weight using conventional free radical polymerization. For the sake of clarity, the term "low molecular weight" as used herein refers to molecular weights in the range of approximately 10,000 to 30,000. Such a low molecular weight is achieved by carefully monitoring and adjusting the reaction conditions, and generally by carrying out the reaction in the presence of a chain transfer agent such as dodecyl mercaptan. There is a clear relationship between intrinsic viscosity and molecular weight, and it has been found within the scope of the invention that monomers polymerized to intrinsic viscosity in the range of 0.1 to 0.4 (measured in a 9: 1 mixture of tetrahydrofuran and alcohol) are generally preferred. In this embodiment, the low molecular weight polymer is mixed and then dissolved in either the polyol prior to reaction with the isocyanate component, or the low molecular weight polymer is dissolved in the urethane prepolymer already formed. In either case, the low molecular weight polymer is combined with the isocyanate-terminated urethane prepolymer in a proportion such that the reactive, curable hot melt adhesive contains about 5-90% urethane prepolymer and 95-10% low molecular weight polymer. The low molecular weight polymer should be stored and handled carefully to avoid contamination of the polymer with ambient moisture or other factors that may affect the stability of the prepolymer system.

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91081 7 mouths. The resulting hot melt adhesive can then be applied to the hot bondable substrate using techniques known to those skilled in the art. The urethane-based hot melt adhesive cures over time at ambient humidity to form a crosslinked product with crosslinks.

According to an alternative process for preparing the urethane prepolymers of the invention, about 2-90% by weight of ethylenically unsaturated monomers are combined with a polyol used at 10-98% by weight and polymerized therein using conventional free radical polymerization techniques in the presence of a chain transfer agent such as dodecyl. a low molecular weight polymer dissolved in a polyol. After polymerization of the ethylenically unsaturated monomers, polyisocyanate and other possible ingredients necessary for the urethane prepolymer formation reaction are added to the mixture, and said reaction is carried out using a conventional condensation method for polymerization. In this way, the resulting isocyanate-terminated urethane prepolymer forms the reactive, curable hot-melt adhesive described above containing about 5-90% urethane prepolymer and 95-10% low molecular weight polymer, and this adhesive can be applied as a melt to the substrate as it cures over time at ambient humidity. forming a crosslinked product.

The low molecular weight polymer can also be polymerized in the presence of an already formed isocyanate-terminated urethane prep polymer. The disadvantage of this method is that the prepolymer has to be heated unnecessarily during the polymerization of the acrylic, which heating can lead to branching, increased viscosity, depletion of the necessary isocyanate groups and possible gelation. Although all of these disadvantages can be controlled by adjustment, the conditions must be adjusted more carefully compared to the polymerization of urethane components θ without isocyanate groups. When the reaction is carried out in a polyol or other component without isocyanate groups, the advantage is also the lower viscosities of the reaction and the lower possibility of being exposed to isocyanate fumes, since more modest heating is sufficient.

As mentioned above, the resulting hot melt adhesives, which are solid at room temperature, have a suitable coating viscosity in the range of 3000 to 50,000 cps at 120 ° C (corresponding approximately to the range of 1500 to 25,000 cps at 135 ° C). and 10,000 to 100,000 cps at 108 ° C, so that no other adhesion promoters or plasticizers need to be added to these adhesives to achieve such coating viscosities, however, it should be noted that small amounts of adhesion promoter or plasticizer may be added to the adhesive as long as they are not present. adversely affect the desired adhesive properties.

Not only do the adhesives cure to form a strong, heat-resistant bond, but they also have a high initial adhesive and cohesive strength, so the doped structure can be handled easily, even before curing, and can be further processed effortlessly. Thus, adhesives can be used in a wide variety of applications where hot melt adhesives are commonly used, especially in applications that require good heat resistance. Such applications requiring good heat resistance include, but are not limited to, processing and sterilizing operations such as, but not limited to, lamination, bookbinding, labeling of bottles and containers, manufacture of automotive interiors, manufacture of non-woven products for healthcare.

It is assumed that these improved properties are due in part to the formation of semi-interpenetrating and interpenetrating networks and, in some cases, the formation of a graft polymer. This can result in semi-interpenetrating networks when the urethane prepolymer (thermosetting plastic) is used with a free radical polymerized polymer that does not contain crosslinking groups (thermoplastic). When a free radical polymerized polymer contains crosslinking groups, perfectly interpenetrating networks result. Grafting occurs in the case of certain types of urethane prepolymer components, such as those containing a carbon atom bearing a tertiary hydrogen atom. Such tertiary hydrogen atoms are possible oxidation sites for acrylic or vinyl monomers.

The invention may be further illustrated by the following examples relating to preferred embodiments of the invention, although it is to be understood that these examples are intended solely to illustrate the invention without limiting its objects in any way, unless specifically stated otherwise.

Example I

The one-liter reaction vessel was equipped with a condenser, a gas inlet tube, a slow addition tube, a thermometer, a stirrer and a heating / cooling device. The following components were used in the reaction: 1. Polypropylene glycol (mol. Weight 1000) 257.8 g 2. 1,6-hexanediol, neopentyl glycol adipate (mp. 3000) 88.9 g 3. 1,6-hexanediol, neopentyl glycol adipate (mp. 1000) 29.3 g 4. Butyl methacrylate 17.8 g 5. Butyl methacrylate 94.1 g 6. Methyl methacrylate 9.4 g 7. Methyl methacrylate 53.6 g 10 8 Dodecyl mercaptan 0.68 g 9. Benzoyl peroxide 1.7 g 10. Benzoyl peroxide 0.6 g 11. Methylene bis-phenyl diisocyanate 131.1 g.

The reaction vessel was purged with dry nitrogen, and dry nitrogen was slowly passed below the surface of the reaction mixture throughout the reaction. Components 1, 2, 3, 4, 6, 8 and 9 were added to the vessel and the temperature was raised to 80 ° C. After keeping the vessel at 80 ° C for half an hour, components 5 and 7 were added evenly over one hour. during adding. The reaction mixture was maintained at 80 ° C for an additional three hours, after which component 10 was added. The reaction mixture was further maintained at 80 ° C for 2 hours, and component 11 was added; then the temperature was raised to 100 ° C where it was maintained for three hours. At this point, a vacuum of 120-130 millimeters was drawn into the vessel for 20-30 minutes, and the reaction mixture was poured hot from the vessel.

Properties: proportion of methacrylate polymer,% 25% ratio of butyl methacrylate to methyl methacrylate 64: 36 proportion of urethane prepolymer,% 75% proportion of isocyanate groups,% 1,9% viscosity at 100 ° C 64 000 cps viscosity 120 ° C: at 25 ° C 2550 cps viscosity at room temperature fixed limit viscosity in a 9: 1 mixture of tetrahydrofuran and ethanol 0.18 color aqueous pale to very light amber brightness clear very cloudy urethane prepolymer calculated molecular weight 3315

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91081 11 isocyanate index 1, 6.

Example II

Here, the procedure was as in Example I, but the viscosity of the system was calculated by reducing the molecular weight of the urethane prepolymer as an alternative to reducing the molecular weight of the methacrylate resin. All factors were the same except for the following:

Components: A B

Butyl methacrylate 18.0 g 18.0 g

Butyl methacrylate 102.0 g 102.0 g

Methyl methacrylate 10, 1 g 10, 1 g

Methyl methacrylate 57.4 g 57.4 g

Dodecyl mercaptan 0, 63 g 0, 72 g

Benzoyl peroxide 1.8 g 1.8 g

Methylene bis-phenyl diisocyanate 168.6 g 168.6 g

Features were:

A B

Proportion of methacrylate polymer,% 25% 25%

Butyl methacrylate to methyl methacrylate ratio 64:36 64:36

Proportion of urethane-based prepolymer,% 75% 75%

Proportion of isocyanate groups,% 3, 1% 3, 3%

Viscosity at 100 ° C 53000 cps 51000 cps

Viscosity at 120 ° C was not determined at 7062 cps

Viscosity at room temperature solid solid

Raj viscosity, THF / EtOH, 9: 1 0, 18 0, 15 Color from watery white to very light amber

Brightness from very slightly to cloudy 12

Calculated molecular weight of urethane prepolymer 2032 1909

Isocyanate index 2.0 2.0

Example III

This example shows the preparation of a urethane prepolymer. This prepolymer consists of 70% polypropylene glycol having a molecular weight of 1000 and 30% 1,6-hexane-diol-neopentyl glycol adipate diol having a molecular weight of 2000, this combination containing as much methylene-bis phenyl diisocyanate to give an NCO content of 2% in the prepolymer.

components:

Polypropylene glycol (molecular weight 1000) 350.0 1,6-hexane-diol-neopentyl glycol adipate diol (molecular weight 2000) 150.0

Methylene bis-phenyl diisocyanate 166.4.

Method: The one-liter reaction vessel was equipped with a condenser, a gas inlet tube, a thermometer, a stirrer, and a heating and cooling device. The reaction vessel was purged with dry nitrogen, and dry nitrogen was slowly passed through the vessel. The polyols were added to the vessel and the temperature was raised to 80 ° C. At this point, diisocyanate was added and the reaction mixture was heated to 100 ° C and maintained at this temperature for 4 hours. After a heating step of 4 hours, the reaction mixture was poured hot from the vessel.

The properties of the urethane prepolymer were:

Proportion of isocyanate groups,% 2, 3%

Viscosity at 100 ° C 3200 cps

Viscosity at room temperature 800,000 cps

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91081 13 Color very light amber

Brightness clear

Isocyanate index 1, 6

Example IV (Comparative) This example illustrates the preparation of a hot melt adhesive according to U.S. Patent No. 3,931,077 using a mixture of a polyurethane prepolymer, a thermoplastic resin and an adhesion promoter.

Prepolymer from Example III 60 CRL 715 (copolymer of 35% n-butyl acrylate and 65% ethylene with a melt index of 70 from USI) PRL 300 (terpene-phenol resin with a softening point of 108 ° C) from Reichhold Chemical)

The urethane prepolymer was placed in a three-necked flask and heated to 167 ° F in a dry nitrogen gas atmosphere, the other two components were added, and stirring was continued under a nitrogen atmosphere until the components were dissolved. This adhesive is abbreviated IVA.

A second hot melt adhesive (abbreviated IVB) was formed as described above using 10 parts of Exxon EX 170 (25% vinyl acetate, 75% ethylene, melt index 2400); 25 parts of PRL-300 and 65 parts of the urethane prepolymer of Example III.

Testing

The following experiments have been developed to characterize the adhesives of the invention and to measure their effectiveness.

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Tensile strength and elongation of cured free films: In this test, the strength and elasticity of the film are measured. The tensile strength and the degree of elongation are proportional to the usefulness of the material as an adhesive. In general, a material having a high tensile strength and adequate elongation has better adhesive performance than a material having one or both of said properties is poor.

In this experiment, films with a thickness of about 3 to 5 mils were cast from the melt on a low energy surface. (Films of this order of magnitude had to be used because heavier films develop too much from the cavity as they harden.) The films were cured by being exposed to the atmosphere for one week in a room at a constant temperature of 22 ° C and 50% relative humidity.

Infectivity test; Samples were prepared using a variety of flexible substrates by coating the substrate with a 1.0-inch-thick layer of molten adhesive, and immediately depositing it on a 3/8-inch chipboard by cold-pressing the layer for 10 minutes at about 5 psi. All samples were allowed to cure or cross-bind for 1 week. They then underwent a 90 * peel mi s test with a removal rate a of 12 inches per minute.

Heat Resistance: Because most hot melt adhesives are thermoplastics that lose their shape or become flowable when exposed to temperatures above 82 ° C, a number of elevated temperature shear stress tests have been developed to determine the ability to resist flow, deformation or deformation. at temperatures up to 175 * C.

In this experiment, a bare aluminum foil with a thickness of 5 mils was added to a 3/8 inch chipboard.

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91081 15 parts, the strength of the adhesive joint with the applied adhesive layer having a thickness of 1 thousandth of an inch. All samples were cured for one week. The samples were placed in a convection oven at 108 ° C, loaded with one kilogram per square inch (1 kg / inch). They were kept at this temperature for 15 minutes, after which the temperature was raised to 120 ° C, where they were observed for 15 minutes. Thereafter, the temperature was raised at regular intervals until the joint was found to break.

Fresh strength: In this test, the strength of the bond is measured immediately after application and bonding of the adhesive. This is an important test because it determines the strength of the uncured material before curing. The fresh strength of the material must be sufficient to keep the substrates together after bonding and as the material hardens at ambient humidity. Fresh strength or immediate bond strength before curing as well as cure rate are very important properties in manufacturing or layering processes before complete curing.

In this experiment, molten adhesive samples were coated at 120 ° C to a layer of exactly 1.0-thousandth of a thickness on Mylar films with a thickness of 2-thousandths of an inch, and then immediately attached to an aluminum foil with a thickness of 5-thousandths of an inch. The resulting laminate Mylar / glue / foil was then peeled immediately, and after said times, using an Instron tester at 12 inches / min.

Comparison of viscosity at 120 * C Example Visc. 120 * C (Thermocel) I 11625 cps IIB 5500 cps III 1138 cps IVA 9000 cps IVB 5000 cps 16

Comparison of tensile strength and elongation

Example Final Tensile Strength Elongation,% I 1350 psi 460% IIB 3250 psi 440% III 667 psi 440% IVA 960 psi 520% IVB 200 psi 1400%

Of note are the low tensile strengths in Examples III and IV, as well as the better tensile strengths and good elongation values in Examples I and II, which represent the adhesives according to the invention. Also, the higher tensile strength in Example II should be noted, which corresponds to a higher NCO content.

Results of the adhesion test

embossed

Bare aluminum Woodgrain white mine foil, Mylar vinyl vinyl, 5 mil_ 2 mil 6 mil 4 mil

Eg I 6.5 lbs * "1.4 lbs' · * 5.5 lbs' · * 4.5 lbs' · *

Eg II A 5, 5 lbs' · * 1, 5 lbs 6, 5 lbs' · * 5, 5 lbs' · *

Eg Ill 1, 7 lbs 1, 8 lbs 6, 6 lbs' · * 5, 2 lbs

Eg IV A 7.6 lbs '* 0.4 lbs 0.2 lbs 4.0 lbs' *

Eg IV B 6, 7 lbs' * 0, 9 lbs 7, 0 lbs' * 4, 5 lbs' * FT = fiber tearing

The adhesives of Examples I and II bound excellently to most substrates, and the adhesive of Example I adhered excellently to all substrates including Mylar. It should be noted that the cause of bond breakage was fiber rupture (FT). The uppermost fibers of the chipboard, which served as a substrate, were stuck to the glue. The adhesive of Example II could not adhere to Mylar alone. The adhesive of Example III did not adhere to the foil or Mylar; The adhesive of Example 91081 17 IVA did not adhere to Mylar or vinyl, and the adhesive of Example IVB did not adhere to Mylar.

Comparing heat resistance

Example 108 "C 120 * C 134 'C 150 * C 162' C 175 * C

I OK OK OK OK 13 min to rupture II (A & B) OK OK OK OK OK 8 h III OK OK OK 9 min to rupture IV A 1 min to rupture IV B 1 min to rupture This experiment illustrates the adhesives of Examples IVA and IVB. (prior art adhesives) poor heat * resistance, and good heat resistance of the adhesives of Examples I and II. The best heat resistance was obtained with the adhesive according to Example II, which has a high NCO content.

Comparison of bond strength

Example Example Example Example Example

I_ II (A) III IVA IVB

Immediate (fresh) 300 g 170 g 20 g 120 g 2100 g 1 hour 375 g 170 g 25 g 205 g 1800 g 2 hours 375 g 172 g 65 g 206 g 1850 g 3 hours 363 g 180 g 125 g 375 g 1800 g 24 hours 1200 g 680 g 700 g 425 g 1900 g 48 hours 1200 g E / ME / M 272 g 908 g 1 week 1500 g E / ME / M 91 g 771 g E / M »Not specified 18

The above test results clearly show the better properties of the heat sealants of the present invention compared to the prepolymer to which no acrylic was added and the material of U.S. Patent No. 3,931,077 in terms of bond strength and heat resistance, especially after aging.

The following examples illustrate modifications of the most preferred embodiment of the invention to illustrate various aspects of the invention.

Example V

The procedure of Example I was repeated except that 0.8 g of dodecyl mercaptan was used instead of 0.68 g. This change was made to reduce the molecular weight of the methacrylate copolymer that is part of the product (which is stated as a lower intrinsic viscosity), and thus to lower the viscosity of the product.

Features were:

Proportion of methacrylate polymer,% 25%

The ratio between butyl methacrylate and methyl methacrylate is 64:36

Proportion of urethane prepolymer,% 75%

Proportion of isocyanate groups,% 2, 0%

Viscosity at 100 ° C 18000 cps

Viscosity at room temperature solid

Raj viscosity in a 9: 1 mixture of tetrahydrofuran and ethanol 0, 15 Color from aqueous white to very light amber

Brightness from very slightly to slightly cloudy

Isocyanate index 1, 6.

91081 19

Example VI

The experiment was carried out as described in Example I, except that the amount of dodecyl mercaptan used as a chain transfer agent was reduced to 0.54 g to increase the molecular weight of the methacrylate polymer and thus increase the viscosity compared to Example II.

Features were:

Proportion of methacrylate polymer,% 25%

The ratio of butyl methacrylate to methyl methacrylate is 64:36

Proportion of urethane prepolymer,% 75%

Proportion of isocyanate groups,% 3, 0%

Viscosity at 100 ° C 72000 cps

Viscosity at 120 ° C 16250 cps

Viscosity at room temperature solid

Intrinsic viscosity in a 9: 1 mixture of tetrahydrofuran and ethanol 0.15 Color from aqueous white to very light amber

Brightness from very slightly to slightly cloudy

Isocyanate index 1.6.

Example VII

In this example, the following significant changes were made to Example I: 1) The ratio of methacrylate polymer to urethane prepolymer was changed from 25/75 to 30/70; 2) The ratio of butyl methacrylate to methyl methacrylate was changed from 64/36 to 80/20; 3) The composition of the urethane prepolymer was changed from polypropylene glycol / 1,6-hexane diol and neopentyl glycol adipate t-methylene bis-phenyl diisocyanate to polypropylene glycol / methylene bis-phenyl diisocyanate.

This example was carried out according to Example I, except that the following amounts were used:

components:

Polypropylene glycol (mol. Weight 1000) 300.3

Butyl methacrylate 23.0

Butyl methacrylate 130.6

Methyl methacrylate 5, 8

Methyl methacrylate 32, 6

Dodecyl mercaptan 0.3 g

Benzoyl peroxide 1.9 g

Benzoyl peroxide 0.6 g

Methylene bis-phenyl diisocyanate 147.8 g

Features were:

Proportion of methacrylate polymer,% 300%

The ratio of butyl methacrylate to methyl methacrylate is 80:20

Proportion of urethane prepolymer,% 70.0%

Proportion of isocyanate groups,% 3, 9%

Viscosity at 100 ° C 104,000 cps

Viscosity at room temperature solid

Raj viscosity in THF / EtOH (9: 1) 0.19 Color aqueous white

Brightness from clear to very cloudy

Isocyanate index 2.0.

Example VIII

This example illustrates the use of a different acrylate monomer. The example was carried out as in Example I, but using the following components.

components:

Polypropylene glycol (mol. Weight 1000) 326.4 g

Butyl acrylate 150.0 g

Dodecyl mercaptan 0.3 g

Benzoyl peroxide 2.0 g

Methylene bis-phenyl diisocyanate 122.8 g

Features:

Acrylate polymer content,% 25, 0%

Proportion of urethane prepolymer,% 75.0%

Proportion of isocyanate groups,% 1.7%

Viscosity at 100 ° C 7200 cps

Viscosity at room temperature> 2.8x10 *

Viscosity in THF / EtOH (9: 1) 0.15 Color light brown

Brightness cloudy

Isocyanate index 1.5

Example IX

In this example, an isocyanate other than methylene bis-phenyl diisocyanate was used. The example was carried out as in Example I, except using the following components.

components:

Polypropylene glycol (mol. Weight 1000) 275.7 g 1,6-hexanediol, neopentyl adipate diol (mol. Weight 2000) 118, 2 g

Butyl methacrylate 17.8 g

Butyl methacrylate 94.1 g 22

Methyl methacrylate 9, 1 g

Methyl methacrylate 53.6 g

Dodecyl mercaptan 0.68 g

Benzoyl peroxide 1/7 g

Benzoyl peroxide 0.6 g

Methylene bis-cyclohexyl diisocyanate 137.4 g

Dibutyl tin dilaurate 0.08 g.

Features:

Proportion of methacrylate polymer,% 25%

The ratio of butyl methacrylate to methyl methacrylate is 64:36

Proportion of urethane prepolymer,% 75%

Proportion of isocyanate groups,% 2, 2%

Viscosity at 120 * C 5000 cps (estimated)

Viscosity at room temperature solid

Intrinsic viscosity in THF / EtOH 9: 1 0, 13 Color watery hard

Brightness clear

Isocyanate index 1, 6.

Example X

In this example, a catalyst was added to the reaction mixture to accelerate curing. The reaction was now carried out according to Example I.

components:

Polypropylene glycol (mol. Weight 1000) 275.7 g 1,6-hexanediol, neopentyl adipate diol (mol. Weight 2000) 118, 2 g

Butyl methacrylate 17.8 g

Butyl methacrylate 94, 1 g

Methyl methacrylate 9, 4 g

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91081 23

Methyl methacrylate 53.6 g

Dodecyl mercaptan 0.68 g

Benteoyl peroxide 1.7 g

Benzoyl peroxide 0.6 g

Methylene bis-phenyl diisocyanate 131.1 g

Dibutyl tin dilaurate 0.30 g

My new s:

Proportion of methacrylate polymer,% 25%

The ratio of butyl methacrylate to methyl methacrylate is 64:36

Proportion of urethane prepolymer,% 75%

Isocyanate groups,% 1, 9%

Viscosity at 100 * C 84000 cps (estimated)

Viscosity at room temperature solid

Intrinsic viscosity in THF / EtOH 9: 1 0.17 Color from aqueous white to very light amber

Brightness from very little to cloudy

Isocyanate index 1, 6.

Example XI

In this example, the procedure of Example I was repeated, however, replacing the acrylate comonomers with styrene. The components and features were as follows:

Components:%

Polypropylene glycol (mol. Weight 1000) 275.7 g 1,6-hexanediol, neopentyl adipate diol (mol. Weight 2000) 118, 2 g

Styrene 174, 9

Dodecyl mercaptan 0.68 g

Benzoyl peroxide 1.7 g 24

Benzoyl peroxide 0.6 g

Methylene bis-phenyl diisocyanate 131, 1 g

My new s:

Proportion of styrene polymer,% 25%

Proportion of urethane prepolymer,% 75%

Proportion of isocyanate groups,% 1.7%

Viscosity at room temperature solid

Intrinsic viscosity in THF / EtOH (9: 1) 0.23 Color yellowish

Brightness cloudy

Isocyanate index 1, 6

Example XII

Again, the procedure of Example I was repeated, but replacing the acrylate copolymer with vinyl acetate. The components and features were as follows:

components:

Polypropylene glycol (mol. Weight 1000) 275.7 g 1,6-hexanediol, neopentyl adipate diol (mol. Weight 2000) 118, 2 g

Vinyl acetate 174.9 g

Dodecyl mercaptan 0.68 g

Benzoyl peroxide 1/7 g

Benzoyl peroxide 0.6 g

Methylene bis-phenyl diisocyanate 137.4 g

My femininity:

Proportion of vinyl acetate polymer,% 25%

Proportion of urethane prepolymer,% 75%

Proportion of isocyanate groups,% 2, 0%

Viscosity at 121 ° C 1800 cps

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91081 25

Viscosity at room temperature> 4 x 10 «cps

Intrinsic viscosity in THF / EtOH (9: 1) 0.15 Color light sea resin

Brightness cloudy

Isocyanate index 1, 6

Example XIII

This example illustrates the addition of a commercially available low molecular weight polymer to a urethane prepolymer to produce a hot melt adhesive according to an alternative embodiment of the invention. Elvacite 2013 is a copolymer of 64% butyl methacrylate and 36% methyl methacrylate with an intrinsic viscosity of 0.2, available from DuPont. Elvacite was dried in a vacuum desiccator for 24 hours immediately before use.

components:

Polypropylene glycol (mol. Weight 1000) 472.9 g 1,6-hexanediol neopentyl glycol adipate (mol. Weight 2000) 202.7 g

Elvacite 2013 300.0 g

Methylene bis-phenyl diisocyanate 224.9 g

Method:

The polyols and Elvacite 2013 were added to the vessel and heated at 100 ° C until the Elvacite was dissolved. At this point, methylene bisphenyl diisocyanate was added to the reaction mixture and maintained at 100 ° C for 3 hours. After 3 hours at 100 ° C, the mixture was poured hot from the vessel. The samples had the following characteristics:

My femininity:

Proportion of methyl acrylate polymer,% 25.0%

Proportion of urethane prepolymer,% 75, 0%

Proportion of isocyanate groups,% 2, 0%

Viscosity at 100 ° C 86000 cps

Viscosity at 120 ° C 8000 cps

Viscosity at room temperature solid

Intrinsic viscosity in THF / EtOH (9: 1) 0.25 Color aqueous white

Brightness from very little to cloudy

Isocyanate index 1.6

Test results:

Final tensile strength: 1700 psi

Elongation,% 400%

Viscosity stability at 120 ° C original 8000 cps after 8 hours 12125 cps

Bond strength (foil / mylar) immediately 908 g 1 hour 1025 g 2 hours 1040 g 3 hours 1100 g 24 hours 1750 g

Adhesion test (peeling at 90 * C)

Mylar 1.7 pounds

Foil, 5 mil 5, 5 pounds

Woodgrain Vinyl 6.9 Pounds (FT)

White vinyl 5.7 pounds (FT) li 91081 27 Heat resistance (2 psi):

180 'C OK

120 * C OK

134 * C OK

150 * C OK

162 * C 10 minutes to break

Example XIV

In order to compare the initial strength properties, other adhesives (numbered 1 to 4) were also prepared according to the invention using the above procedures. Five other adhesives were prepared in U.S. Patent No. 3,968,089 to Cuscurida et al. , according to Examples II, III, IV, V and IX (adhesives 5-9, respectively). Table I shows the components used and the quantities of raw materials in grams. The intrinsic viscosity, isocyanate index and viscosity of the adhesives at room temperature were determined and the results are shown in Table II.

Table II

Viscosity

Intrinsic viscosity Isocyanate index at room temperature

Adhesive (IV) __ (l. L) _ weather, cps_ 1 0, 11 1.9 Solid 2 0.18 1.6 Fixed 3 0, 15 1.6 Fixed 4 0.17 1.6 Fixed 5 0.09 12, 9 74000 6 0, 09 12.0 17440 7 0, 07 16, 5 1960 8 0, 09 21, 1 1520 9 0.09 13, 1 31000 28

The following experimental procedures were used to determine the performance depending on the initial strength (fresh strength) of the adhesives. The test results are shown in Table lii.

peeling:

Woodgrain vinyl, which acts as a substrate, was applied with a 1.0-1.5-inch-thick layer of adhesive heated to about 120 ° C (directly or by heat transfer), and the substrate was compressed with a 3/8-inch-thick chipboard 3-5 seconds in a press using a 5 pound weight. The sample was peeled at 90 ° C at a rate of 5 inches / minute using a peeling tester, e.g., Instron Tester (sample dimensions: strip width 1/2 inch, length 3-4 inches). The sample was peeled immediately after removal from the press, i.e. within 1-2 minutes).

Lap Shear: Aluminum foil with a thickness of 5 mils was coated with a 2-3 inch thick layer of adhesive heated to approximately 120 ° C (directly or by heat transfer). The coated aluminum was pressed together with a 3/8 inch chipboard for 3-5 seconds in a press using a weight of about 5 pounds. The sample was drawn at 180 ° C in a tensile tester (e.g., Instron Tester) at a rate of 0.2 inches per minute. (The binding area in the sample was 1/2 "x 1/2".) The drawing of the sample was carried out immediately after removal from the press, i.e. within 1-2 minutes.

Table III

Adhesive Shear-Adhesive Peelability (lbs, / inch) Strength (lbs, / inch) _ 1 4.2 ... 4.4 31.5 2 4, 0.. . 4, 0 18, 2 3 1, 0.. . 1, 19, 3 4 1, 4.. . 1, 7 15, 1 5 alc. bond strength is missing initial. bond strength missing 6 initial. bond strength is missing initial. bond strength is missing

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91081 29 7 original bond strength is missing initial. bond strength is missing 8 initial. bond strength is missing initial. bond strength missing 9 initial. bond strength is missing initial. bond strength is missing

It will be apparent that various changes and modifications may be practiced in embodiments of the invention without departing from the scope of the invention as defined in the appended claims. Accordingly, the foregoing description is intended to illustrate the invention without limiting it in any way.

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Claims (8)

A solvent-free polyurethane-based hot-melt adhesive mixture which is solid at room temperature, characterized in that it comprises an isocyanate-terminated polyurethane prepolymer which contains a polymer of ethylenically unsaturated monomer in a polyolate-free polyurethane a concentration of 0.25-15% and having an isocyanate index greater than 1 but not more than about 2; said adhesive being prepared by the steps of: 1) combining 2-90% by weight of an ethylenically unsaturated, active hydrogen-free monomer with 10-98% by weight of a polyol; 2. The mixture of step (1) is polymerized using a free radical based polymerization technique as well as chain transfer agents to obtain low molecular weight polymers; 3. Sufficient polyisocyanate is added to the mixture to achieve the desired isocyanate content and isocyanate index, and the polymerization is carried out using a condensation-based technique. Hot melt adhesive mixture according to Claim 1, characterized in that the ethylenically unsaturated monomer is selected from the group consisting of C 1 -C 18 esters, vinyl esters and ethers of acrylic and methacrylic acids, fumarates, maleates, styrene, acrylonitrile and their acrylonitrile. Hot melt adhesive mixture according to Claim 1, characterized in that the urethane prepolymer is prepared by polymerizing a diol and a diisocyanate using a condensation technique. Il 91081 Hot melt adhesive mixture according to Claim 1, characterized in that the ethylenically unsaturated monomers are polymerized so as to have an intrinsic viscosity of 0, 1 to 0.4. Hot melt adhesive composition according to Claim 1, characterized in that the polyol is selected from the group consisting of substituted or unsubstituted polyalkylene ether glycols or polyhydroxy polyalkylene ethers, polyhydroxy polyesters and the polyisocyanate is selected from the group consisting of ethylene diisocyanate, ethylene diisocyanate, propylene diisocyanate, butylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, toluene diisocyanate, -1,4-diisocyanate, cyclohexylene 1,2-diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,2-diphenylpropane-4,4'-diisocyanate, p-phenylenediisocyanate, m -phenylene diisocyanate, xylylene diisocyanate, 1,4-naphthylene diisocyanate, 1,5-naphthylene diisocyanate, di phenyl 4,4'-diisocyanate, azobenzene-4,4'-diisocyanate, diphenylsulfone 4,4'-diisocyanate, dichlorohexamethylene diisocyanate, furfurylidene diisocyanate, 1-chlorobenzene , 4-diisocyanate, 4,4 ', 4 "-triisocyanato-triphenylmethane, 1,3,5-triisocyanato-benzene, 2,4,6-triisocyanato-toluene and 4,4' - dimethyldiphenylmethane-2,2 ', 5,5-tetraisocyanate. Hot melt adhesive mixture according to Claim 1, characterized in that the free isocyanate content is less than 4%. Hot melt adhesive mixture according to Claim 6, characterized in that the free isocyanate content is less than 1%. A process for preparing a solvent-free, polyurethane-based hot-melt adhesive mixture at room temperature having a viscosity of 3000 to 50,000 cps at 120 ° C without added adhesion promoters or plasticizers, characterized in that the process comprises the steps of: ) 2-90% by weight of ethylenically unsaturated, active hydrogen-free monomer is combined with 10-98% of polyol; 2. The mixture of step (1) is polymerized using a free radical based polymerization technique as well as chain transfer agents to provide a low molecular weight polymer; 3. Add enough polyisocyanate to the mixture to give an isocyanate content of 0.25-15% and an isocyanate index of more than 1 but less than about 2, and the mixture is polymerized using a condensation technique. I! 91081