FI91081C - 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 base for the manufacture of wood-based products 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 cohesive and adhesive strength by the addition of low molecular weight acrylic resins. 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.

Hot melt adhesives are 100% solid materials that do not contain 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.

In order to obtain the desired physical properties, most of the hot melt adhesives are formed of thermoplastic (thermoplastic) materials which are used as a melt at high temperatures and which cure rapidly upon cooling. Unfortunately, their 2 thermoplastic nature also results in a bond that is sensitive to heat, and which bond may break even under the influence of moderate heat.

Hot melt adhesive compositions which are applied as a melt, which cool 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 original adhesive strength of polyurethane-based hotmelt adhesives by adding certain thermoplastic resins, for example, according to U.S. Patent 3,931,007, issued January 6, 1976 to Uchigaki et al. However, these thermoplastic resins are generally materials with a high molecular weight (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. Although the addition of these plasticizers and tackifiers reduces the hot viscosity of the formed adhesive, the relatively high amounts required adversely affect the adhesion properties of the polyurethane 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 polymers formed from ethylenically unsaturated, active hydrogen-free monomers having a low molecular weight of 120 ° C provides a hot melt adhesive which is solid at room temperature At the temperature of C without the addition of other adhesion promoters or plasticizers. These adhesives have good initial cohesive strength and good strength after aging of the cured bond. In addition, when these adhesives are used, improved properties are achieved with a wide variety of substrates, including difficult-to-bond substrates such as polyvinyl chloride, Mylar (DuPont polyester film), and aluminum.

The low molecular weight polymer can be added to the polyol prior to reaction with the isocyanate components, or it can be added to the preformed prepolymer. The products of the invention can also be formed by simultaneously polymerizing a urethane prepolymer and ethylenically unsaturated monomers. The polyurethane precursor polymer can also be polymerized ethylenically in 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 subsequently polymerized with the resulting mixture using conventional condensation methods. The advantage of the latter polymerization process is that the molecular weight (as determined by intrinsic viscosity) of the resulting vinyl polymer can be excellently controlled, and this process additionally provides a polymer that does not disturb. In addition, costs are significantly reduced due to the simplification of handling, the reduction of the materials required and the avoidance of temporary packaging and storage.

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, for example methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, n-propyl or isopropyl acrylate, but also corresponding 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 copolymed with them. The choice of the particular monomer (s) depends largely 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 selected in a suitable manner to form structural adhesives, conductive adhesives, and the like.

Urethane prepolymers are compounds traditionally used in the art to make 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 the 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, toluene diisocyanate, isocyanate, cyclohexylene 1,4-diisocyanate, cyclohexylene 1,2-diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,2-diphenylpropane-4,4'-diisocyanate, p- Phenylene diisocyanate, m-Phenylene diisocyanate, Xylylene diisocyanate, 1,4-naphthylene diisocyanate, 1,5-naphthylene diisocyanate, Diphenyl 4,4'-diisocyanate, Athebenzene-4 , 4'-diisocyanate, diphenylsulfone-4,4'-diisocyanate, dichlorohexamethylene diisocyanate, furfurylidene diisocyanate, 1-chlorobenzene-2,4-diisocyanate, 4, 4 ', 4 " -triisocyanato-triphenylmethane, 1,3,5-triisocyanato-benzene, 2,4,6-triisocyanato-toluene, 4,4'-dimethyldiphenylme dane-2, 2 ', 5, 5-tetraisocyanate, and the like.

The proportions of polyisocyanate and polyol components to be combined are selected such 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. By keeping the isocyanate index low, the final free isocyanate content in the final, hot melt adhesive mixture is reduced to about 4%. preferably less than 1%. It should be noted that higher levels of free isocyanate present adversely affect the melt formulation because 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 original 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 5-55% 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, it is to be understood that 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 can be achieved by carefully monitoring and controlling 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 particularly 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% of the low molecular weight urethane prepolymer and 95-10% of the low molecular weight polymer. The low molecular weight polymer should be stored and handled carefully to avoid contamination of the polymer with ambient humidity or other factors that may affect the stability of the prepolymer system.

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91081 7 mouths. Thereafter, the resulting hot melt adhesive can be applied as a hot melt to the substrate to be bonded 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 comprising slurry bonds.

According to an alternative process for the preparation of the urethane prepolymers of the invention, about 2 to 90% by weight of the ethylenically unsaturated monomers are combined with the polyol used in the range of 10 to 98% by weight and polymerized therein using conventional free radical polymerizers. to obtain a low molecular weight polymer dissolved in the polyol. After the polymerization of the ethylenically unsaturated monomers, polyisocyanate and any other constituents which are essential for the formation of the urethane prepolymer are added to the mixture, and said reaction is carried out using conventional condensation for the polymerization. In this way, the resulting isocyanate-terminated urethane prepolymer forms the reactive, curable hot-melt adhesive described above containing about 5-90% of the urethane prepolymer and 95-10% of the low molecular weight polymer being crosslinked. forming a crosslinked product.

The low molecular weight polymer can also be polymerized in the presence of the isocyanate-terminated urethane precursor polymer already formed. 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 required isocyanate groups and possible gelation. Although all of these disadvantages can be kept under control, the conditions must be adjusted more carefully compared to the polymerization of urethane components is which are free of isocyanate groups. When the reaction is carried out in polyol or other components which do not contain isocyanate groups, the advantage is then also the lower viscosities of the reaction and the lower possibility of being exposed to isocyanate vapors, 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 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 a small amount of adhesion promoter or softener may be added to the adhesive. The desired adhesive properties are not adversely affected by the presence of låsnå.

Adhesives not only cure to form a strong, heat-resistant bond, but also have a high initial adhesive and cohesive strength, so that the cured structure can be handled easily, even before curing, and further processed effortlessly. Thus, straw 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 nonwovens for medical use, and the like.

It is hypothesized 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 (thermoplastic) is used with a free radical polymerized polymer that does not contain crosslinking groups (thermoplastic). When the free radical polymerized polymer does not contain crosslinking groups, the result is completely interpenetrating networks. 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 sources of 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 the purpose of these examples is merely 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 pipe, a slow-addition pipe, 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. The reaction mixture was kept at 80 ° C for a further 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 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 at 120 ° C at 25 ° C viscosity at room temperature fixed limit viscosity in a 9: 1 mixture of tetrahydrofuran and ethanol 0.18 color aqueous to very light amber brightness clear to 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 bulk 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%

Ratio of butyl methacrylate to methyl methacrylate 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, in THF / EtOH, 9: 1 0, 18 0, 15 Color from watery white to very light amber

Brightness from bright to very cloudy 12

Calculated molecular weight of urethane prepolymer 2032 1909

Isocyanate index 2.0 2.0

Example III

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

Components t:

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 apparatus. 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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13 91081 Color very light amber

Brightness clear iBocyanate 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, combined 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 in a nitrogen atmosphere until the component! t had dissolved. The abbreviation IVA is used for this adhesive.

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 usability of the material as an adhesive. In general, a material having a high tensile strength and adequate elongation has a better adhesive performance than a material having one or both of said properties is poor.

In this experiment, films having 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 as the cavities harden.) The films were cured by being exposed to the atmosphere for one week in a room at a constant temperature of 22 ° C at 50% relative humidity.

Infectivity test; Samples were prepared using various 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 were then subjected to a 90 * crushing test at a picking speed of 12 inches per minute.

Heat resistance: Since most hot melt adhesives are thermoplastics that lose their shape or become flowable when exposed to temperatures above 82 ° C, a number of shear stress tests have been developed within the scope of the invention. at high temperatures up to 175 * C.

In this experiment, a bare aluminum foil with a thickness of 5 inches 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 inch of soak (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 joining and as the material hardens at ambient humidity. Fresh strength or immediate bond strength prior to curing as well as cure rate are very important properties in manufacturing or deposition processes prior to complete curing.

In this experiment, the molten adhesive samples were coated at 120 ° C to an exact thickness of 1.0 mils on Mylar films having a thickness of 2 mils and then optionally bonded to an aluminum foil having a thickness of 5 mils. The resulting laminate Mylar / glue / foil was then peeled immediately, as well as 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%

Note 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 note the higher tensile strength in Example II, which corresponds to a higher NCO concentration.

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 Ibs * "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 the bond breakage was fiber rupture (FT). The superficial fibers of the chipboard acting as a substrate must adhere to the adhesive. 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 fracture II (A & B) OK OK OK OK OK 8 h III OK OK OK 9 min to fracture IV A 1 min to fracture IV B 1 min to fracture This experiment illustrates the adhesives of Examples IVA and IVB. (prior art adhesives) poor heat resistance, as well as good heat resistance of the adhesives of Examples I and II. The best heat resistance was obtained with the adhesive of Example II / with a high NCO content.

Comparison of bond strength

Example Example Example Example Example

I_ II (A) III IVA IVB

Vålitdn (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 hot melts of the present invention compared to the prepolymer to which no acrylic was added, as well as to the material of U.S. Pat. No. 3,931,077, in terms of bond strength and heat resistance.

The following examples illustrate modifications of the most preferred embodiment of the invention to illustrate various features 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 (as determined by the lower intrinsic viscosity), and thus to calculate the viscosity of the product i.

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 clear to very 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 to increase the viscosity of the oils compared to eBememark II.

The peculiarities were:

Proportion of methacrylate polymer,% 25%

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

Proportion of urethane lysolymer,% 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 pale amber

Brightness from clear to very 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-hexanediol 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 quantities 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 very bright to slightly cloudy

Isocyanate index 2.0.

Example VIII

This example illustrates the use of a different acrylate monomer 91081 21 m. 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

Omlnalsuudet:

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 *

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

Brightness cloudy

Isocyanate index 1.5

Example IX

In this example, a non-methylene bis-phenyl diisocyanate other than methylene cyanate was used. The example was carried out as in Example I, but 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 was 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: 10, 13 Color aqueous white

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 di-diocyanate 131.1 g

Dibutyl tin dilaurate 0.30 g

Ominai s new:

Proportion of methacrylate polymer,% 25%

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

Proportion of urethane prepolymer,% 75%

Proportion of isocyanate groups,% 1, 9%

Viscosity at 100 * C 84000 cps (estimated)

Solidity at room temperature fixed

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

Brightness from bright to very 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

Here 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 new s:

Proportion of vinyl acetate polymer,% 25%

Proportion of urethane prepolymer,% 75%

Proportion of isocyanate groups,% 2, 0%

Viscosity at 121 ° C 1800 cps

II

91081 25

Viscosity at room temperature> 4 x 10 «cps

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

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 make a hot melt adhesive according to an alternative embodiment of the invention. Elvacite 2013 is a copolymer containing 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 with it.

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

Go to:

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 it was kept at 100 ° C for 3 hours. Then, after keeping the mixture at 100 ° C for 3 hours, it was poured hot from the vessel. The samples had the following characteristics:

Features:

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 8 ° C 8000 cps

Viscosity at room temperature solid

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

Brightness from bright to very little

Isocyanate index 1.6

Experienced branches:

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 (of which numbers 1-4 are used) were also prepared according to the invention using the above procedures. Five other adhesives were prepared in U.S. Patent 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 amounts 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 room temperature Adhesive (IV) __ (l. I) _ så, cps_ 1 0, 11 1.9 Solid 2 0.18 1.6 Solid 3 0, 15 1.6 Solid 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 original strength (fresh strength) of the adhesives. The test results are shown in Table III.

peeling:

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

Lap Shear: Aluminum foil with a thickness of 5 mils was coated with a layer of 2-3 mils 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 a temperature of 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 sample was drawn immediately after removal from the press, i.e. within 1-2 minutes.

Table III

Limit Shear-Llima Hatch (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

II

91081 29 7 original bond strength is missing initial. bond strength is missing 8 initial. bond strength is missing initial. bond strength missing 9 al kup. bond strength missing al kup. 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. Thus, the foregoing description is intended only to illustrate the invention without, however, 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, which comprises a polyurethane prepolymer of an isocyanate-terminated polyurethane prepolymer which is ethylene-saturated with ethylene. an isocyanate content of 0.25-15% and having an isocyanate index greater than 1 but not more than about 2; said adhesive being prepared in the steps of: 1) 2-90% by weight of an ethylenically unsaturated, active hydrogen-free monomer combined 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 technique. Hot melt adhesive composition according to Claim 1, characterized in that the ethylenically unsaturated monomer is selected from the group consisting of C 1 -C 18 esters of acrylic and methacrylic acids, vinyl esters and ethers, fumarates, maleate, styrene, styrene . 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-based technique. II 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 mixture 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 ether esters, polyhydroxy-polyesters, polyethylenes of propylene and propylene or propylene monosubstituted esters, and the polyisocyanate is selected from the group consisting of ethylene diisocyanate, ethylidene isocyanate, propylene diisocyanate, butylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, toluene cyclohexylene 1,4-diisocyanate, cyclohexylene 1,2-diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,2-diphenylpropane-4,4'-diisocyanate, p-phenylenedioisocyanate cyanate, m-phenylenediisocyanate, xylylene diisocyanate, 1,4-naphthylene diisocyanate, 1,5-naphthylene diisocyanate diphenyl 4,4'-diisocyanate, azobenzene-4,4'-diisocyanate, diphenylsulfone 4,4'-diisocyanate, dichlorohexamethylene diisocyanate, furfurylidene diisocyanate, -chlorobenzene-2,4-diisocyanate, 4,4 ', 4 "-triisocyanato-triphenylmethane, 1,3,5-triisocyanato-benzene, 2,4,4,6-triisocyanato-toluene and 4 From 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 and room temperature solid hot melt adhesive mixture having a viscosity of 3000 to 50,000 cps at 120 ° C without the addition of adhesion promoters or plasticizers, characterized in that , wherein: 1) 2-90% by weight of an ethylenically unsaturated, active hydrogen-free monomer is combined with 10-98% 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 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