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US-12617984-B2 - Hydrophilic hotmelt adhesive

US12617984B2US 12617984 B2US12617984 B2US 12617984B2US-12617984-B2

Abstract

A hotmelt adhesive comprising a metallocene-catalyzed polyolefin and a hydrophilic melt additive. The adhesive is permanently hydrophilic and can be in particular used to bond components of a disposable hygienic article such as a diaper.

Inventors

  • Torsten Lindner
  • Gültekin Erdem

Assignees

  • THE PROCTER & GAMBLE COMPANY

Dates

Publication Date
20260505
Application Date
20220420
Priority Date
20210420

Claims (19)

  1. 1 . A hydrophilic hotmelt adhesive comprising by weight of the hotmelt adhesive: from about 30% to about 99% of a metallocene-catalyzed polyolefin, wherein the metallocene-catalyzed polyolefin has a peak molecular weight in the range of from about 10,000 g/mol to about 130,000 g/mol, wherein the peak molecular weight is measured according to the Peak Molecular Weight (Mp) Measurement Method, from about 0.1% to about 10% of a hydrophilic melt additive, wherein the hydrophilic melt additive comprises a first wetting agent and a second wetting agent, and wherein the second wetting agent comprises a water-soluble, nonionic, nonhydrolyzable polyoxyalkylene-modified organosilicone polymer, and from about 0% to about 40% of a tackifier.
  2. 2 . The hydrophilic hotmelt adhesive according to claim 1 , wherein the metallocene-catalyzed polyolefin is propylene-based.
  3. 3 . The hydrophilic hotmelt adhesive according to claim 1 , wherein the hotmelt adhesive has a viscosity at 170° C. in the range of from about 100 mPa·s to about 10,000 mPa·s, as measured by Viscosity Test Method.
  4. 4 . The hydrophilic hotmelt adhesive according to claim 1 , wherein the first wetting agent is a water insoluble nonionic alkoxylated alkyl phenol.
  5. 5 . The hydrophilic hotmelt adhesive according to claim 1 , wherein the hydrophilic melt additive comprises an ethoxylated alcohol.
  6. 6 . The hydrophilic hotmelt adhesive according to claim 5 , wherein the ethoxylated alcohol has the formula: with x ranging from 2 to 100 and y ranging from 12 to 24.
  7. 7 . The hydrophilic hotmelt adhesive according to claim 1 , wherein the hotmelt adhesive exhibits a Fresh Film Contact Angle and an Aged film Contact Angle with distilled water of less than 70 about degrees, as measured by the Contact Angle Method.
  8. 8 . The hydrophilic hotmelt adhesive according to claim 1 , wherein the hotmelt adhesive has a storage modulus (G′) higher than about 300,000 Pa at 37° C., wherein the storage modulus is measured with the Oscillatory Rheometry Test Method.
  9. 9 . An absorbent article comprising a bond formed by the hydrophilic hotmelt adhesive according to claim 1 , wherein the article comprises a topsheet, an absorbent core, a backsheet, and optionally an acquisition layer, wherein the absorbent core optionally comprises an absorbent material and a core wrap, wherein the bond formed by the hydrophilic hotmelt adhesive is between two layers selected from: the topsheet and the optional acquisition layer; or the optional acquisition layer and the absorbent core; or the topsheet and the absorbent core; or the core wrap and the absorbent material.
  10. 10 . An absorbent article comprising a bond formed by the hydrophilic hotmelt adhesive according to claim 1 , wherein the article comprises an absorbent core, the absorbent core comprising an absorbent material layer sandwiched between the top side and the bottom side of a core wrap, the top side being closer to the topsheet than the bottom side, and wherein the hydrophilic hotmelt adhesive is disposed between the top side and the absorbent material layer, and the hydrophilic hotmelt adhesive at least partially immobilizes the absorbent material within the core wrap.
  11. 11 . An absorbent article comprising a bond formed by the hydrophilic hotmelt adhesive according to claim 1 , the article comprising a three-dimensional laminate comprising a first layer and a second layer wherein the first layer is intermittently bonded to the second layer by the hotmelt adhesive so that the first layer comprises a plurality of protrusions not bonded to the second layer, wherein the three-dimensional laminate is a topsheet and the first layer comprises cotton fibers.
  12. 12 . An absorbent article comprising a bond formed by the hydrophilic hotmelt adhesive according to claim 1 , wherein the bond is between a first nonwoven and another component of the article, and wherein the first nonwoven is bonded by the hydrophilic hotmelt adhesive to at least one selected from a second nonwoven, cellulose fibers, or superabsorbent particles.
  13. 13 . A substrate comprising a coating, wherein the coating is a hotmelt adhesive according to claim 1 .
  14. 14 . The hydrophilic hotmelt adhesive according to claim 1 , wherein the metallocene-catalyzed polyolefin has an enthalpy of fusion of from 5 J/g to 45 J/g.
  15. 15 . The hydrophilic hotmelt adhesive according to claim 1 , wherein the hydrophilic hotmelt adhesive is substantially free of tackifier.
  16. 16 . The hydrophilic hotmelt adhesive according to claim 1 , wherein the metallocene-catalyzed polyolefin has a peak molecular weight in the range of from about 10,000 g/mol to about 70,000 g/mol, wherein the peak molecular weight is measured according to the Peak Molecular Weight (Mp) Measurement Method.
  17. 17 . The hydrophilic hotmelt adhesive according to claim 1 , wherein the hydrophilic hotmelt adhesive is permanently hydrophilic.
  18. 18 . The hydrophilic hotmelt adhesive according to claim 1 , wherein the hydrophilic hotmelt adhesive comprises a blend of two or more metallocene-catalyzed polyolefins.
  19. 19 . An absorbent article comprising a bond formed by a hydrophilic hotmelt adhesive, wherein the article comprises a topsheet, an absorbent core, a backsheet, and optionally an acquisition layer, wherein the absorbent core optionally comprises an absorbent material and a core wrap, wherein the bond formed by the hydrophilic hotmelt adhesive is between two layers selected from: the topsheet and the optional acquisition layer; or the optional acquisition layer and the absorbent core; or the topsheet and the absorbent core; or the core wrap and the absorbent material; wherein the hotmelt adhesive comprises, by weight: from about 30% to about 99% of a metallocene-catalyzed polyolefin, and from about 0.1% to about 10% of a hydrophilic melt additive, and from about 0% to about 40% of a tackifier, wherein the metallocene-catalyzed polyolefin has a peak molecular weight in the range of from about 10,000 g/mol to about 70,000 g/mol, wherein the peak molecular weight is measured according to the Peak Molecular Weight (Mp) Measurement Method, and wherein the hydrophilic melt additive comprises a first wetting agent and a second wetting agent, and wherein the second wetting agent comprises a water-soluble, nonionic, nonhydrolyzable polyoxyalkylene-modified organosilicone polymer; and wherein the hotmelt adhesive comprises a plasticizer, wherein the plasticizer comprises up to about 20% of the hotmelt adhesive.

Description

CROSS REFERENCE TO RELATED APPLICATION This application claims the benefit, under 35 U.S.C. § 119(b), of PCT Patent Application Serial No. PCT/CN2021/088387, filed on Apr. 20, 2021, the entire disclosure of which is incorporated herein by reference. FIELD OF THE INVENTION The invention relates to hotmelt adhesives having hydrophilic properties. The hydrophilic hotmelt adhesives of the invention can be used in personal hygiene absorbent articles, such as diapers or feminine protections. The hydrophilic hotmelt adhesives facilitate the transfer of a fluid such a urine transfer from one layer of the article to another layer. The hydrophilic hotmelt adhesives may be used to bond a nonwoven to another layer, such as a second nonwoven or an absorbent material. BACKGROUND OF THE INVENTION Nonwovens are used as topsheet, acquisition layer or core wrap in disposable articles such as diapers, adult incontinence products and sanitary napkins. In these articles, it is necessary to adhere the nonwoven to another layer of the article. This second layer may be another nonwoven, a tissue, or an unrelated material such as an absorbent material. A commonly employed technique to bond the components of the absorbent article is the use of a hotmelt adhesive. Hotmelt adhesives allow for cost and time efficient manufacturing, since there is no evaporation step necessary as is the case for water based or solvent based adhesive systems. Suitable hotmelt adhesives must possess excellent adhesion to the substrates involved. For nonwoven applications they must also possess good flexibility, no staining or bleed through, suitable viscosity, set speed and open time to function on commercially available equipment, and acceptable thermal aging properties. In personal hygiene article such as disposable diapers, sanitary napkins and bed pad constructions, it is desired to draw the moisture away from the body and into the absorbent core as quickly as possible after the article is wetted. Nonwovens which have been hydrophillically treated have been proposed. WO 2017/156234 A1 (P&G, Lindner et al.) discloses material webs comprise a hydrophobic or hydrophilic melt additive that can be activated in localized areas by thermal energy. WO 2018/165511 A1 (P&G, Lindner et al.) discloses a permeable nonwoven comprising fibers and/or filaments made of a polymer matrix comprising a hydrophilic melt additive and/or a tactile modifying melt additive. Spunbond PP nonwoven comprising hydrophilic melt additives are for examples disclosed in U.S. Pat. No. 6,146,757 (Techmer). It has also been proposed to use hotmelt adhesives having the ability to facilitate the transmission of an insulting liquid from a nonwoven layer towards the absorbent material, in order to achieve quicker fluid transmission. WO 00/00229 (P&G, Lindner et al.) discloses hygienic articles comprising an oil resistant, hydrophilic adhesive. The formula of the adhesive or its permanency is however not disclosed. U.S. Pat. No. 6,380,292 B1 (Bostik) discloses hydrophilic hotmelt adhesive compositions suitable for nonwoven disposable articles which are prepared by blending various adhesive components with a surfactant, including high amount of tackifiers. Commercially available tackified hotmelt adhesives are typically found to be not permanently hydrophilic, i.e. they lose their hydrophilicity over time or under conditions of accelerated aging. There is a need for hydrophilic hotmelt adhesive compositions that are safe for use in personal absorbent articles, retain their hydrophilic properties over time and are cost-effective. SUMMARY OF THE INVENTION In a first aspect, the invention is directed to a hydrophilic hotmelt adhesive comprising a metallocene-catalyzed polyolefin and a hydrophilic melt additive. The metallocene-catalyzed polyolefin may be in particular a propylene-ethylene copolymer. The metallocene-catalyzed polyolefins may in particular have a peak molecular weight ranging from 10,000 g/mol to 130,000 g/mol, wherein the peak molecular weight is measured according to the Peak Molecular Weight (Mp) Measurement Method disclosed herein. Suitable hydrophilic melt additives are amphiphilic molecules, comprising a hydrophilic group and a hydrophobic group. Preferred, non-limiting, commercial examples of propylene-ethylene copolymers and hydrophilic melt additives are described further below in the description. The invention provides hotmelt adhesives that can exhibit a Fresh Film Contact Angle and an Aged Film Contact Angle with distilled water of less than 70 degrees, preferably of less than 50 degrees, as measured by the Contact Angle Test described herein. In a second aspect, the invention is directed to a personal hygiene absorbent article, such as a diaper or an adult incontinence product, comprising the hydrophilic hotmelt adhesive of the invention. The hotmelt adhesive can be in particular used to directly bond a pair of layers selected from (not exhaustive list): the topsheet and