MXPA96004585A - Film adhesive by - Google Patents

Abstract

The present invention relates to a laminated structure comprising a microporous thermoplastic film containing liquid additive, a continuous or intermittent hot melt adhesive coating layer wherein the microporous film containing liquid additive at the contact points of the adhesive has a L value of at least 70, the hot melt adhesive is characterized in that it comprises: 100 parts of a polymer or copolymer or polybutylene mixture wherein the copolymer comprises from 1 to 30 mole percent of an alpha olefin comonomer from C2 to C3 or C5 to C8, 0 to 300 parts of a solid adhesive resin compatible with the polybutylene phase, 0 to 20 parts of liquid adhesive, 0 to 40 parts of a plasticizer and 0 to 25 parts of a particulate filler

Description

ADHESIVE FOR POROSA FILM BACKGROUND AND FIELD OF THE INVENTION The present invention relates to hot melt construction adhesives for adhering porous thermoplastic films to a substrate. Typically, the disposable absorbent articles require an external liquid impermeable polymeric film or sheet to prevent the absorbed liquid from passing through the article to come into contact with the users' clothing or skin. Since this layer of liquid impervious film is typically not breathable, does not allow the passage of wet steam, the articles may become hot and uncomfortable, occasionally leading to a skin rash. In this regard, microporous films impervious to liquids that make the absorbent article breathable have been proposed. A common disposable microporous film is filled with filler particles in amounts greater than about 30 percent. However, those particles filled with respirable particles are less desirable in terms of the softness, feel and contamination of the tape. REF: 23167 U.S. Patent No. 4,902,553 proposes a microporous polymeric film permeable to steam free of rattle to be used as an external liquid impermeable backing sheet for a disposable absorbent product such as a diaper or an incontinent product. This patent proposes to use a microporous film impervious to liquids but permeable to steam, which could allow the wet steam to escape by reducing the tendency of the absorbent product to produce a rash, such as the rash of diapers or other types of skin irritation. The microporous film is a soft film, free of rattle, permeable to vapor, impermeable to liquids. The rattle-free nature of the film is achieved by the inclusion of liquid additive materials that reduce rattling in the film and by reliefs. Other patents that describe a microporous film containing liquid additive include U.S. Patent Nos. 4,539,256; 4,609,584 / 4,726,989 or 4,824,719. The microporous films described in these patents are all suitable for use as a liquid impermeable film, microporous, in a hygienic or absorbent article. However, one problem with these films is that the films have a tendency to change from opaque to translucent to the contact points of the hot melt adhesive. This is particularly noticeable and objectionable when the films adhere to a substrate with the conventional hot melt adhesives in an intermittent adhesive pattern. This results in an aesthetically unpleasant product which also has a weakened level of addition between the microporous film and the substrate. This is a particular problem when the liquid additive is a plasticizing oil, such as mineral oil. Although numerous formulations of conventional hot melt pressure sensitive adhesives have been evaluated by the Applicant to adhere these microporous films to conventional substrates all have resulted in uniform clarification of the film at the contact points of the adhesive. This clarification of the film also tends to diffuse towards the adjacent areas of the film that are not in direct contact with the adhesive. After extensive research and selection the Applicant has discovered adhesives that overcome the problems identified above particularly with respect to microporous films containing prior liquid additive.

BRIEF DESCRIPTION OF THE DRAWING Figure 1 is a graph comparing the operation of the adhesives of the invention with the adhesives of the prior art.

BRIEF DESCRIPTION OF THE INVENTION The present invention provides a sheet of a microporous film, preferably containing a liquid additive such as a plasticizing oil, which adheres to a substrate, such as an absorbent pad, by means of a hot melt adhesive composition, particularly suitable for the application of adhesives in multiple lines or intermittently, without clarification of the microporous film. The sheet of the invention uses a hot melt adhesive composition based on a crystalline polybutylene polymer that provides a hot melt adhesive having an open-air drying time of at least 5 seconds and preferably more than 1 minute. The hot melt adhesive preferably comprises 100 parts of polybutylene, polybutylene copolymer or mixtures thereof, 0 to 300 parts of a compatible solid adhesive resin, 0 to 40 parts of a plasticizer, and optionally 0 to 50 parts of a filler and 0 to 15 parts of an additive to reduce the viscosity of the polymer.

DESCRIPTION OF THE PREFERRED MODALITIES The hot melt adhesive of the sheet of the invention provides high adhesion to shearing and shedding to microporous films, particularly a microporous film containing liquid additive such as that described in U.S. Patent Nos. 4,902,553; 4,539,256; 4,609.5874; 4,726,989; Or 4,824,719, without making the films clear or becoming opaque or translucent. A microporous film in the sheet having an L value of at least 80 maintains an L value of at least 70, preferably at least 75 and more preferably at least 80, 15 days after thermal aging, in the contact points of the adhesive with the hot melt adhesive and in areas adjacent to the contact points of the adhesive. Adhesion to the T-detachment of the microporous film to a substrate in the sheet is at least 20 g / 25 mm, and preferably at least 50 g / 25 mm, with 2,000 grams of application of downward movement and days of thermal aging. The microporous film containing preferred liquid additive in the sheet, described in the above patents comprises a microporous film formed by dissolving a crystallizable polymeric material in a liquid additive at a temperature above the melting temperature of the polymeric material and forming this melt in a film, such as by extrusion. The homogeneous solution was then allowed to cool at a suitable rate to cause the crystallizable polymer to crystallize in a different interconnected phase, the polymer is incompatible with the additive at room temperature or conditions of use. The material of the film of different phase was then oriented uniaxially or ultiaxially, creating a film with micropores, all of which now maintain the liquid additive in a different phase. The liquid additive is preferably one that exhibits plasticizing properties. Potential additive materials include saturated hydrocarbons such as mineral oil, glycerin, petroleum jelly, low molecular weight polyethylene, polyethylene oxide, polypropylene oxide, tetramethylene oxide, mild carbowax, plasticizing oils and the like. Preferred additive materials are plasticizing oils, mineral oil being particularly preferred because of its relatively low cost and excellent film-forming properties. The crystallizable polymeric material is preferably olefinic, such as polyolefins, or condensation polymers such as polyesters or polyamides. More preferred are polyolefins such as crystalline isotactic polypropylene, polyethylene, polybutylene, polyethylpentene, copolymers, block polymers and modified versions thereof. The additive liquid can be used in a fluctuating amount of about 5 to 80 weight percent of the formed film, preferably 5 to 50 percent, and more preferably 10 to 30 percent. Discussions of crystallizable polymers and phase separation additives are also found in U.S. Patent Nos. 4,247,498 and 4,100,238. For example, for isotactic polypropylene, those patents describe the use of separable additives in phases such as poly-1-butene, polyethylene wax, low molecular weight polyethylene, alcohols, aldehydes, amines, esters such as methylene benzoate. , ethers such as diphenyl ether, hydrocarbons such as trans-stilbene or ketones. Nucleating agents such as those described in US Patent Nos. 4,824,718 and 4,726,989 to produce the uniform crystallization of the polymeric material after cooling. These nucleating agents are preferably at least one primary agent, generally an organic acid or derivative, which dissolves the liquid additive at a temperature at least 10 ° C higher than the crystalline transition temperature of the thermoplastic polymer, and which is used in amounts of 0.05 to 5 percent of the system, and optionally a secondary inert nucleating agent, which is used at approximately the same concentration. The secondary inert nucleating agent usually comprises an inorganic particulate material such as talc, titanium dioxide, calcium carbonate, magnesium carbonate, barium carbonate, magnesium sulphide, barium sulfide, and the like. Suitable organic acids include mono or polyacid, for example, carboxylic acids, sulfonic acids, phosphonic acids and solid organic alcohols such as dibenzylidene sorbitol. Preferred organic acids include adipic acid and succinic acid, and a preferred secondary nucleating agent is talc. After precipitation of the thermoplastic crystallizable polymer, the film can be used, without orientation or orientation, with an elasticity ratio in at least one direction from 0 to 3, preferably from 1.5 to 2.5.

When the film is not oriented, the liquid additive is preferably washed from the film. Generally, the thickness of the microporous film is from 5 to 250 microns, preferably from 20 to 200 microns. Comparatively thinner films are preferred in terms of cost and increased wet vapor permeability. Thicker films provide an improved tensile performance against more aggressive adhesives. The hot melt adhesive polymer is an adhesive that has an open-air drying time of the adhesive of at least 5 seconds, more often more than one minute, more likely more than 5 minutes. For conventional hot-melt adhesive application, the viscosity of the adhesive is preferably less than 10,000 centipoise (cp), more preferably less than 5,000 cp. For extrusion application such as melt blown the viscosity of the adhesive can be as high as 50,000 cp or greater. The crystalline thermoplastic polymer used in the hot melt adhesive formulation is preferably a 1-butene homopolymer or copolymer or a mixture thereof. Preferred is a 1-butene copolymer with 1-30 mol percent of a comonomer of an alpha olefin, preferably polyethylene, polypropylene, 2-butene, or a C5 to C8 alpha olefin. The comonomer is preferably in one mole percent between 2 and 15 percent based on the entire polymer with the preferred comonomer being an ethylene monomer. These polymers and copolymers are discussed in U.S. Patent No. 4,937,138. Amorphous polymers (eg, polypropylene, polyhexene and polyokene) provide adhesives that clear the microporous film. The adhesive components for the crystallizable polymer based on adhesives generally comprise solid adhesive resins used alone or in combination with a liquid adhesive resin and / or a liquid plasticizer. Preferably, the adhesive resin is selected from the group of resins at least partially compatible with the elastomeric polymer or block copolymer. Suitable plasticizers for use in the hot melt adhesive composition of the sheet include the phase-separable adhesives in the microporous film containing liquid additive including waxes such as petroleum waxes, Fischer-Tropsch waxes, microcrystalline waxes, polyolefin waxes and plasticizing oils such as naphthionic oils, paraffinic oils, aromatic oils, polybutene oil and mineral oils. Any of the waxes or plasticizing oils or other plasticizers can be used in amounts of up to 40 parts per 100 parts of the crystallizable polymer. Preferably, low molecular weight plasticizers (average MW of less than 500) or having a significant proportion of liquid species at temperatures lower than 50 ° C, such as plasticizing oils or paraffin wax or liquid adhesives, are used at levels below 20. parts per 100 parts of polymer. Preferably, high molecular weight plasticizers (average MW greater than 1000) or having very few liquid species at less than 50 ° C are used, such as waxes or plasticizers of higher melting temperature at levels of minus 35 parts to 100 parts of polymer. Some waxes and / or plasticizers may be added to reduce the viscosity of the adhesive to a preferred range. Additives that reduce the molecular weight, or viscosity of the polymer, such as free radical initiators such as peroxides (eg, 2,5-dimethyl-2,5-bis (t-butyl peroxy) -hein-3) can also be added to the polymer. or transition metal catalysts and the like, preferably in amounts of 0.01 to 50 parts to 100 parts of polymer, more preferably 0.01 to 5 parts. Fillers may be added to the adhesive formulation to increase the opacity or L value of the microporous film at the contact points of the adhesive. The fillers are particularly useful for decreasing the viscosity of the hot melt adhesives of the invention, which tends to slightly reduce the value of L of the microporous film at the contact points of the adhesive, but not in the adjacent areas of the microporous film. Useful fillers include the particles used for the microporous film filled with particles, titanium dioxide is preferred in terms of cost and opacity. Preferably the fillers are used in amounts ranging from 0 to 25 parts to 100 parts of polymer, more preferably less than 15 parts. It was also contemplated that nucleating agents can be added to the preferred adhesive formulation in small amounts to increase crystallization and crystallization rate. Such nucleating agents could include isotactic polypropylene, stearamide or 1-naphthalene acetamide in amounts ranging from 0.01 to 10 parts, preferably from 0.1 to 5 parts, more preferably less than 1 part, based on the total adhesive formulation. Other nucleating agents known in the art are described in U.S. Patent No. 4,937,128. The preferred polybutylene copolymer can be used in a mixture with polybutylene homopolymer, preferably in a range of 1/10 to 10/1 polymer to copolymer, more preferably in a ratio of 2/10 to 10/2. The polybutylene copolymers can also be modified by incorporating functional monomers or by subsequently grafting with portions such as maleic anhydride or other modifying agents that react by free radicals. The microporous film adhesive sheet will generally comprise a substrate layer which will eventually be a breathable fabric or other material including conventional nonwoven fabrics such as non-woven fabrics, woven fabrics, absorbent fibrous papers or materials joined by spinning, sewing, melting hot, loaded or otherwise where the construction of the sheet is a component in a disposable absorbent product such as a diaper, feminine sanitary towel or adult incontinent product. In a preferred embodiment, the sheet is dotted or with a relief pattern formed by heat, pressure, ultrasonic, or the like. The relief softens the touch of the film, while at the same time partially masking any slight lightening of the film.

Preparation of the Adhesive The adhesives were prepared by premixing the adhesive components, feeding them into a single screw extruder and mixing / melting the mixture at temperatures of at least 350 ° F (177 ° C). The adhesive mixtures were collected in a thin tray and subsequently cut into small pieces, which were then used to spray the hot melt. The adhesive compositions that were evaluated are summarized in Tables I and II. The Brookfield viscosity data for the adhesives are reported in Table I.

Examples 1-8 and 11-18 The samples of adhesive A-Q (except for the adhesive H) were melted and cut with a blade on the microporous film at the thicknesses indicated in Tables III and IV. The microporous film used was prepared in accordance with US Pat. Nos. 4,539,256 and 4,726,989. The composition of the microporous film was 70 weight percent polypropylene (# 5D45, 0.65 MFI polypropylene available from Shell Chemical Co.), 29.9 weight percent mineral oil (Amoco hite # 31 USP Grade, available from Amoco Oil Co.), and 0.1 weight percent dibenzylidene sorbitol nucleating agent (Millad 3905, available from Milliken Chemical). The microporous film thicknesses were approximately 1.8 mils (45 microns). The samples were tested and the opacity data obtained were summarized in Tables III and IV. In Figure I the opacity values of examples 1 and 8, comparative examples 9 and 10 and a base film x are presented graphically with the thermally aged film at 50 ° C for 15 days.

Comparative Examples 9 and 10 For comparison, two commercially available hot melt adhesives were evaluated. Ecomelt # H-406, and National Starch # 34-5566 (both styrene-butadiene copolymer adhesives adhered with a hydrocarbon type adhesive), were coated on the microporous film in a similar manner to that described above. The opacity data obtained for those comparative examples are summarized in Table III.

TABLE I C 1 Measure at 170 ° C after at least 1 hour of heating, using a Brookfield digital viscometer model # DV-1 according to ASTM # D2556, TABLE II TABLE III 00 TABLE IV V-3 Examples 19-32 Approximately 1000 grams of the adhesive was melted at 330 ° F (166 ° C) in the melting tank of a hot melt adhesive sprayer (Series 3500 from Nordson, available from Nordson Corp.) and then sprayed through a nozzle 0.012 inch (0.305 mm) in diameter on the microporous film substrate (from Examples 1-18) creating a spiral adhesive pattern on the film having an approximate width of one inch (2.54 cm). Three rows of adhesive were coated in the longitudinal or machine direction of a six inch (15.2 cm) wide sample of the microporous film. Adhesive rows were separated by areas approximately one inch (2.54 cm) wide from regions not coated with adhesives. A non-woven fabric was immediately placed on top of the adhesive surface by hand and the microporous / adhesive / non-woven film sheet was pressed down by hand, passing twice, using a rubber roller of 4.5 pounds (2 kg). The non-woven fabric used was typical of that used for the inner top sheet of a disposable diaper, a polypropylene joined by knit stitching having a basis weight of 0. 8 oz / yd2 (25. 8 gms / m2) (available from International Paper Co.). The sheets were tested for adhesion to the initial T release and thermally aged (at 50 ° C). Adhesion to the initial T release means that the samples were tested within the first three days of preparation of the sheets. The results are summarized in Table V.

Comparative Examples 33-35 For comparison several amorphous polyalphaolefin polymers were evaluated. The polymers evaluated were a propylene homopolymer ("REXTAC ™" 2115 available from Rexene Products Co.), an ethylene-propylene copolymer ("REXTAC ™" 2304 available from Rexene Products Co.), and a butene-propylene copolymer ( "REXTAC ™" 2715 available from Rexene Products Co.). These polymers have crystallization heats of 25, 15, and 6 Joules / gm, respectively, compared to the isotactic polypropylene which had a crystallization heat of 95-100 Joule / gm. The polymers were melted in the sample chamber of a manual hot melt adhesive spray gun and a spiral pattern was sprayed onto microporous film samples identical to those used in Examples 1-18. A nonwoven fabric identical to that used in Examples 1-18 was then immediately placed on top of the adhesive surface by hand. In order to make the three microporous film samples clear, they were put in contact with the amorphous polymers.

TABLE V 1 the sample was aged with heat for 4 days 2 the sample was aged with heat for 2 days Comparative Example 36 The adhesive of Comparative Example 9 ("ECOMELT" H-406) was melted in a tank and mixed with a blue particulate color concentrate to determine if the color of the adhesive could hide the lightening effect that occurs with a conventional adhesive. The adhesive mixture was coated in a pattern on the porous film of examples 1-18 using dot patterns with coatings ranging from 12.5% to 50% of the total surface of the film, and was manually laminated sequentially with a nonwoven. The resulting sheet began film clearance 2-3 days after at room temperature. Although the adhesive points retained their color through the film, the rest of the film, areas not coated with adhesive, became clear with the lightening diffusing from the contact points of the adhesive outward. The addition of particles did not solve the problem of thinning the microporous film when conventional adhesives are used.

Example 37 A polybutylene based on hot-melt adhesives of the formulation; DP-8910 65% Arkon P-100 10%, and Polybutene Oil (Indapol # H-1900) 20% warmed and degraded until it turned light brown in color. This was done to decrease the viscosity of the adhesive to cause a slight lightening of a microporous film. After being washed out, 5% of Ti02 was added to see if the Ti02 could hide any clearing of the porous film after spray coating and thermal aging. The adhesive coated film was laminated on a nonwoven fabric substrate as with all previous samples. Although the resulting sheet showed slight discoloration of the film on the bond lines, there was no discoloration beyond the binding line. DP 8910PC is a polybutylene / polyethylene copolymer (with a content of 6% ethylene) having a crystallinity measured by wide-angle X-rays, available from Shell Chemical Co. "IRGANOX" 1076 is a hindered phenol antioxidant available of Ciba-Geigy.

The "ARKON" P-100 is a solid hydrogenated C9 adhesive resin available from Arakawa Chemical Co. The "PICCOLYTE ™" S-115 is a solid beta pinene adhesive resin available - from Hercules Inc. The N? SCOREZMR "5300 is a solid adhesive resin of hydrogenated hydrocarbons available from Exxon Chemical. "LUPERCOMR" 101-XL is a peroxide available from Elf Atochem 15 North America Inc. "MEKONMR" is a petroleum, microcrystalline, white wax, available from Petrolite . The "UNILIN **" 700 is a saturated alcohol, ? long, linear chain, available from Petrolite. The "POLIWAX" 2000 is a polyethylene wax that has an Mn = 2000 and a melting temperature of 126 ° C available from Petrolite. The "INDAPOLO" H = 1900 is a polybutene oil available from Amoco.

TEST METHODS The following test methods were used to evaluate polybutylene-based construction adhesives for microporous films.

T-Adhesion Adhesion Test The test was carried out at constant temperature and humidity (23 ° C and 50% relative humidity) and the film / microporous nonwoven sheet samples were conditioned for 24 hours before the test. A 1"x 6" (2.5 cm x 12.7 cm) sample of the sheet cut in the cross or cross direction of the sheet was used for the test. Each test sample was cut so that at least one end of the test piece was free of adhesive. The non-woven layer was then placed in the lower jaw of a constant velocity "INSTRON **" tensile tester and the microporous film layer was placed in the upper jaw of the tensile tester. At a head speed of 12 inches (30.5 cm) per minute the force required to detach the microporous film from the non-woven fabric in a T-release mode (180 degrees) was recorded. The force removed to remove the film from the non-woven fabric was reported in grams / 25 mm width and the reported values are an average of at least six tests (two test samples have three separate adhesive regions).

Opacity test The capacity, or white component, of the mircoporous film coated with adhesive was measured to evaluate the adhesive effect of the adhesive on the microporous film. The opacity can be described in terms of its L value of the LAB color test. The value of L was measured using a Spectrum Colorimeter "LABSCAN" * "(Hunter Associates Laboratory, Inc., Reston, VA) using the TAPPI test procedure # T-524. The initial and thermal aging data were obtained. (Up to 7-15 days, at 50 ° C.) The reported values are an average of two tests The different modifications and alterations of this invention will be apparent to those skilled in the art without departing from the scope and spirit of this invention, and this invention should not be restricted to what is set forth herein for illustrative purposes It is noted that with respect to this date, the best method known to the applicant for carrying out the aforementioned invention, is the conventional one for the manufacture of the objects to which it is referred to, the invention having been described as above, property is claimed as contained in the following:

Claims (21)

1. A laminated structure comprising a microporous thermoplastic film containing liquid additive, a continuous or intermittent hot melt adhesive coating layer wherein the microporous film containing liquid additive at the contact points of the adhesive has an L value of at least 70, the hot melt adhesive is characterized in that it comprises; 100 parts of a polymer or copolymer or polybutylene mixture wherein the copolymer comprises from 1 to 30 mol percent of a comonomer of an alpha olefin of C2 to C3 or C5 to C8, 0 to 300 parts of a solid adhesive resin compatible with the polybutylene phase, 0 to 20 parts of liquid adhesive, 0 to 40 parts of a plasticizer and 0 to 25 parts of a particulate filler.

2. The sheet according to claim 1, characterized in that the liquid additive of the layer of the microporous thermoplastic film forms a different phase within the microporous film.

3. The sheet according to claim 2, characterized in that the liquid additive comprises from 5 to 50 weight percent of the film, and the microporous film is oriented.

4. The sheet according to claim 3, characterized in that the liquid additive comprises from 10 to 30 weight percent of the film, and the microporous film is oriented up to 3: 1 in at least one direction.

5. The sheet according to claim 4, characterized in that the liquid additive is mineral oil.

6. The sheet according to any of claims 1 to 5, characterized in that the hot melt adhesive has an open-air drying time of at least 1 minute further comprises 0.01 to 10 parts of an additive to reduce the viscosity of the polymer.

7. The sheet according to claim 6, characterized in that the hot melt adhesive composition has a viscosity of at least 10,000 cp.

8. The sheet in accordance with any of 5 claims 1 to 7, characterized in that the hot melt adhesive composition has a viscosity of at least 5,000 and an open-air drying time of more than 5 minutes.

9. The sheet according to any of claims 1 to 8, characterized in that the microporous film has a value of L of at least 75 at the contact points of the adhesive and a value of L of at least 80 in the areas that It is not in contact with the 5 adhesive.

10. The sheet according to any of claims 1 to 9, characterized in that the hot-melt adhesive further comprises 0 to 50 0 parts of a filler to 100 parts of the adhesive.

11. The sheet according to any of claims 1 to 10, characterized in that the sheet comprises a disposable absorbent article, comprising the microporous film adhered to a structure of the absorbent fibrous material via the hot melt adhesive.

12. The sheet according to any of claims 1 to 11, characterized in that the plasticizer comprises from 0 to 20 parts of a plasticizing oil having an average molecular weight of less than 500.

13. The sheet according to any of claims 1 to 11, characterized in that the adhesive composition comprises from 0 to 35 parts of a plasticizer having an average molecular weight of at least 1000.

14. The sheet according to any of claims 1 to 13, characterized in that the T-detach adhesion of the microporous film of the porous substrate is at least 30 g / 25 mm 15 days after thermal aging and pressing down the adhesive with a roll of 2,000 grams towards the sheet when it is formed.

15. The sheet according to any of claims 1 to 14, characterized in that the T-detachment is at least 50 g / 25 mm.

16. The sheet according to any of claims 1 to 15, characterized in that the plasticizer comprises a microcrystalline wax, a polybutene oil or a polyethylene wax.

17. The sheet according to any of claims 1 to 16, characterized in that the adhesive further comprises 0.01 to 5 parts of a nucleating agent.

18. The sheet according to any of claims 1 to 17, characterized in that the nucleating agent is less than 1 part and wherein the polybutylene is a polybutylene copolymer having from 2 to 13 mol percent alpha-olefin comonomer.

19. The sheet according to claim 18, characterized in that the alpha olefin comonomer is an ethylene monomer.

20. The sheet according to any of claims 1 to 18, characterized in that the sheet further comprises a substrate layer.

21. The sheet according to claim 20, characterized in that the sheet is dotted or has an embossed pattern.