NEW HOT MELT ADHESIVE FOR CONSTRUCTION OF DISPOSABLE NONWOVEN HYGIENE PRODUCT

Abstract

Hot melt adhesive composition comprising: —from 30% to 55% of a composition (A) consisting of 2 copolymers of propylene and ethylene (A1) and (A2), with Mw of less than 100,000 Da, wherein: —(A1) is an essentially amorphous copolymer, with a DSC melt enthalpy of 10 less than 30 J/g; —(A2) is a semicrystalline copolymer with a DSC melt enthalpy of more than 30 J/g; and —the ratio:weight of (A2)/weight of (A1) is from 0.2 to 1.5; —from 20% to 50% of a tackifying resin (B); and 1—from 2% to 25% of a plasticizer (C) consisting of a liquid polybutene oligomer. 2) Process of manufacturing an assembly product, preferably a disposable nonwoven absorbent article, implementing said hot melt adhesive composition.

Claims

1-15. (canceled)

16. Hot melt adhesive composition comprising: from 30% to 55% of a composition (A) comprising 2 thermoplastic unimodal copolymers of propylene and ethylene (A1) and (A2), each having a weight average molecular weight (Mw) of less than 100,000 Da, wherein: (A1) is an essentially amorphous copolymer, with a DSC melt enthalpy of less than 30 J/g; (A2) is a semicrystalline copolymer with a DSC melt enthalpy of more than 30 J/g; wherein a ratio of weight of (A2)/weight of (A1) is from 0.2 to 1.5; from 20% to 50% of a tackifying resin (B); and from 2% to 25% of a plasticizer (C) comprising a liquid polybutene oligomer.

17. Hot melt adhesive composition according to claim 16, wherein (A1) and (A2) are random copolymers of propylene and ethylene having from about 70% by weight to about 99% by weight of propylene.

18. Hot melt adhesive composition according to claim 16, wherein each of (A1) and (A2) include an isotactic polypropylene chain sequence.

19. Hot melt adhesive composition according to claim 16, wherein the weight average molecular weight of (A1) is from about 5,000 to 60,000 Da and the weight average molecular weight of (A2) is from about 10,000 g/mole to about 100,000 Da.

20. Hot melt adhesive composition according to claim 16, wherein (A1) and (A2) each have a melt flow index (MFI) of more than 35 g/10 min.

21. Hot melt adhesive composition according to claim 16, wherein (A1) exhibits a melt enthalpy from 0 J/g to about 30 J/g and (A2) has an enthalpy of melting from about 30 J/g to about 100 J/g.

22. Hot melt adhesive composition according to claim 16, wherein the ratio of weight of (A1)/weight of (A2) within the composition (A) is about 0.5.

23. Hot melt adhesive composition according to claim 16, wherein the tackifying resin (B) is selected among: a) natural and modified rosins; b) glycerol and pentaerythritol esters of natural and modified rosins; c) polyterpene resins; d) phenolic-modified terpene resins; e) aliphatic petroleum hydrocarbon resins (C5) having a Ring and Ball softening point of from about 60° C. to 140° C., and the corresponding hydrogenated derivatives; f) aromatic petroleum hydrocarbons resins (C9) having Ring and Ball softening point of from about 60° C. to 140° C., and the corresponding hydrogenated derivatives; g) aliphatic and/or aromatic petroleum resins (C5/C9) having a Ring and Ball softening point of from about 60° C. to 140° C., and the corresponding hydrogenated derivatives.

24. Hot melt adhesive composition according to claim 16, wherein the softening point of the tackifying resin(s) (B) lies in the range from 90° C. to 125° C.

25. Hot melt adhesive composition according to claim 16, wherein polybutene (C) is a liquid oligomer of one or more monomer units selected from the group consisting of 1-butene, 2-butene and isobutene.

26. Hot melt adhesive composition according to claim 16, wherein polybutene (C) has a kinematic viscosity at 100° C. which is less than about 10,000 centistoke.

27. Hot melt adhesive composition according to claim 16, wherein it comprises: a) from 35% to 55% by weight of the composition (A) comprising copolymers (A1) and (A2) wherein the ratio of weight of (A2)/weight of (A1) is about 0.5; b) from 30% to 40% by weight of the tackifying resin (B); and c) from 15% to 25% by weight of the plasticizer (C).

28. Process of manufacturing an assembly product, comprising: a step (i) of heating at a temperature ranging from 130° C. to 180° C. the hot melt adhesive composition such as defined in claim 16, for at least a period of time long enough to render the hot melt adhesive composition liquid enough to be applied on a substrate, then a step (ii) of coating said composition on a primary substrate, then a step (iii) of putting into contact the coated surface of the primary substrate with the surface of a secondary substrate, so as to form an adhesive joint bonding the two substrates.

29. Assembly product comprising at least two substrates bonded by at least one hot melt adhesive composition such as defined in claim 16.

30. Assembly product according to claim 29, wherein it is a disposable nonwoven absorbent article.

Description

EXAMPLE A (REFERENCE): SBC BASED HMA AND LAMINATE OBTAINED THEREFROM

[0197] A1—Preparation of the HMA:

[0198] The composition of example A in Table 1 is prepared by simple mixing of its ingredients as pointed out above in the detailed description of the invention.

[0199] Its Brookfield viscosity at 135° C. is measured as above and also reported in Table 1.

[0200] A2—Preparation of a Laminate A2 by Means of a Spiral Spray Summit™ Coating Equipment:

[0201] A laminate A2 is prepared as follows.

[0202] Use is made, as a laminating device, of a machine operating continuously at a line speed of approximately 400 m/minute, which machine is sold by NORDSON under the name of Coater CTL 4400.

[0203] In this machine, the coating nozzle is a spiral spray nozzle (NORDSON Summit™).

[0204] The two substrates employed are: [0205] a 20 μm thick breathable PE film which was previously Corona treated on one side, and which has a width of 20 cm, and [0206] a 16 g/m.sup.2 spunbond hydrophobic nonwoven sheet of the same width, which is composed of fibers of polypropylene (PP).

[0207] These two substrates are packaged as a reel with a width of 20 cm.

[0208] The composition of example A is heated in the melting pot at a temperature of 155° C.

[0209] It is then coated on the untreated side of the PE film at the same temperature of 155° C. and at a coating weight of approximately 3 g/m.sup.2.

[0210] The resulting coating pattern is quite adequate and is typical of a good sprayability (and processability). It corresponds to a 2.54 cm wide non continuous layer which is made of an offset spiralled filament, which is centered on said PE film and along an axis which is perpendicular to the axis of the reel.

[0211] Then, at about 0.25 s after coating (open time), the nonwoven (PP) sheet is put into contact with the coated surface of the PE film, by means of a nip roll applying a pressure of 1 bar.

[0212] A3—Peel Measured Initially and after Aging at 23° C. and at 55° C., for Laminate A2:

[0213] The laminate A2 obtained is then packaged as a reel and left for 24 hours at ambient temperature and at 50% relative humidity.

[0214] A rectangular strip measuring 2.54 cm by approximately 10 cm is then cut out in the coated central area of the laminate.

[0215] The two individual substrates are separated, starting from one end of the above rectangular strip (as a test specimen) and over approximately 2 cm.

[0216] The two free ends thus obtained are fixed to two clamping devices respectively connected to a stationary part and a movable part of a tensile testing device which are located on a vertical axis.

[0217] While a drive mechanism communicates, to the movable part, a uniform speed of 300 mm/minute, resulting in the separation of the two substrates, the separated ends of which are gradually displaced along a vertical axis while forming an angle of 180°, the stationary part, connected to a dynamometer, measures the force withstood by the test specimen thus held.

[0218] The result corresponding to the peel after 24 hours at 23° C. (also called “initial peel”), is expressed in N.

[0219] The peel after, respectively, 2 weeks at 23° C. and 4 weeks at 23° C., is measured by repeating the above protocol except that the assembly obtained after lamination is aged during the respective time at 23° C.

[0220] The peel after, respectively, 2 weeks at 55° C. and 4 weeks at 55° C., is measured by repeating the above protocol except that the assembly obtained after lamination is aged during the respective time at 55° C.

[0221] The results are reported in Table 2 below.

[0222] A4—Preparation of a Laminate by Means of a Comb Slot Signature™ Coating Equipment:

[0223] A laminate A4 is prepared by repeating the protocol A2 above, except that the Spiral spray Summit™ coating equipment is replaced by a comb slot Signature™ coating equipment.

[0224] The coating pattern obtained after coating at 155° C. the PE film is typical of a good processability. It corresponds to a 2.54 cm wide non continuous layer which comprises a multiplicity of homogeneously scattered adhesive filaments of variable length. Said non continuous layer is centered on said PE film and along an axis which is perpendicular to the axis of the reel.

[0225] A5—Peel Measured Initially and after Aging at 23° C. and 55° C., for Laminate A4:

[0226] The protocol of A3 above is repeated for laminate A4.

[0227] The results are reported in Table 3.

[0228] A6—Shear Test on a Laminate A6 Comprising 2 Non Woven PP:

[0229] The level of cohesion of the laminate is also assessed by the shear test, the principle of which consists of the determination of the force necessary for the separation by shear of two substrates bonded by the adhesive composition.

[0230] A6.1 Preliminary Preparation of a Laminate A6 Bonded by the Adhesive Composition of Example A:

[0231] Use is made, as a laminating device, of a machine operating continuously at a line speed of approximately 100 m/minute, which machine is sold by NORDSON under the name of Coater CTL 4400.

[0232] In this machine, the coating nozzle is a slot nozzle, NORDSON Slot™.

[0233] The two substrates employed are identical and consist of a 40 g/m.sup.2 melt blown nonwoven sheet with a width of 20 cm composed of fibers of polypropylene (PP).

[0234] These two identical substrates are packaged as a reel with a width of 20 cm.

[0235] The adhesive composition of example A is heated in the melting pot at a temperature of 155° C., then is coated on 2 cm from the right edge of the first substrate, resulting in the deposition over said edge of a continuous layer with a width of 1.5 cm corresponding to an amount of approximately 20 g/m.sup.2, which layer is positioned perpendicular to the axis of the reel.

[0236] The second substrate is then laminated over the first coated substrate, with an open time of about 0.5 s, by means of a nip roll applying a pressure of 1 bar, in such a way that the adhesive layer is 2 cm from its left edge.

[0237] A6.2 Shear:

[0238] The laminate obtained is then packaged as a reel and left for 24 hours at ambient temperature and at 50% relative humidity.

[0239] The laminated substrates with a total width of about 35 cm and assembled by the 1.5 cm wide coated region are then cut out in the cross direction, so as to obtain a test specimen of rectangular shape with a length of approximately 35 cm and a width of 2.54 cm.

[0240] The first substrate of the specimen is then hung secure in an oven at 38° C., while a 500 g weight is attached to the secondary substrate.

[0241] The time after which the assembly fails, corresponding to the shear after 24 hours at ambient temperature, was found to be equal to 29 minutes.

[0242] A7—Preparation of a Laminate A7 by Means of a Spiral Spray Summit™ Coating Equipment:

[0243] A laminate A7 is prepared as follows.

[0244] Use is made, as a laminating device, of a machine operating continuously at a line speed of approximately 200 m/minute, which machine is sold by NORDSON under the name of Coater CTL 4400.

[0245] In this machine, the coating nozzle is a spiral spray nozzle (NORDSON Summit™).

[0246] The two substrates employed are: [0247] a 20 μm thick breathable PE film which has a width of 20 cm, and [0248] a 16 g/m.sup.2 spunbond hydrophilic nonwoven sheet of the same width, which is composed of fibers of polypropylene (PP).

[0249] These two substrates are packaged as a reel with a width of 20 cm.

[0250] The composition of example A is heated in the melting pot at a temperature of 155° C.

[0251] It is then coated on the PE film at the same temperature of 155° C. and at a coating weight of approximately 3 g/m.sup.2.

[0252] The resulting coating pattern is quite adequate and is typical of a good sprayability (and processability). It corresponds to a 2.54 cm wide non continuous layer which is made of an offset spiralled bead, which is centered on said PE film and along an axis which is perpendicular to the axis of the reel.

[0253] Then, at about 0.5 s after coating (open time), the nonwoven (PP) sheet is put into contact with the coated surface of the PE film, by means of a nip roll applying a pressure of 1 bar.

[0254] A8—Peel Measured Initially and after Aging at 23° C. and 55° C., for Laminate A7:

[0255] The protocol of A3 above is repeated for laminate A7.

[0256] The initial peel is reported in Newton in Table 4.

[0257] The peel after storage of, respectively, 1 week at 55° C., 2 weeks at 55° C. and 4 weeks at 55° C. are converted into the relative value of variation of peel versus the initial peel and expressed in % in Table 4.

EXAMPLE 1 (ACCORDING TO THE INVENTION)

[0258] 1. Preparation of the HMA:

[0259] The composition of example 1 reported in Table 1 is prepared as for the composition of example A.

[0260] Its Brookfield viscosity at 135° C. is measured and reported in Table 1.

[0261] 2. Peel Measured Initially and after Aging at 23° C. and at 55° C., for Laminate A2:

[0262] A laminate A2 obtained through Summit™ coating equipment is prepared by repeating the protocol A2 of example A, except that: [0263] the coating composition is replaced by the composition of example 1; and [0264] the coating temperature of 155° C. is replaced by a coating temperature of 130° C. or 145° C.

[0265] For each of these 2 coating temperatures, the resulting coating pattern is just as adequate as the one obtained for the reference example A, and is also typical of a good sprayability (and processability).

[0266] The peels measured initially and after aging at 23° C. and 55° C. are determined on the laminate corresponding to each of the 2 coating temperatures of 130° C. and 145° C., by repeating the protocol A3 above.

[0267] The results are reported in Table 2.

[0268] While peel values greater than 1 N are already quite acceptable, these results show that excellent peels values, greater than 2 N, are obtained, both initially and after 2 or 4 weeks storage at 23° C., for the laminate A2 comprising the HMA of Example 1. These values are at least just as good as those of the laminate A2 comprising the reference SBC based HMA of Example A. These levels are also obtained together with an adequate sprayability (or processability) and, most advantageously, they are achieved at coating temperatures of 130° C. and 145° C., which are well below the coating temperature of 155° C. required for Example A.

[0269] As to the peels obtained after storage at a temperature of 55° C., most of the results are still greater than about 1 N. These values are to be construed as an indicator of the HMA ability to withstand extended storage over time and under variable storage temperatures. On the whole, the peel values for the HMA of Example 1 are quite comparable with those for the reference SBC based HMA of Example A, taking also into account the much lower coating temperatures of 130° C. and 145° C., with respect to the 155° C. coating temperature for Example A.

[0270] 3. Peel Measured Initially and after Aging at 23° C. and 55° C., for Laminate A4:

[0271] A laminate A4 obtained through Signature™ coating equipment is prepared by repeating the protocol A4 of example A, except that: [0272] the coating composition is replaced by the composition of example 1; and [0273] the coating temperature of 155° C. is replaced by a coating temperature of 130° C. or 145° C.

[0274] For each of these 2 coating temperatures, the resulting coating pattern is just as adequate as the one obtained for the reference example A and is also typical of a good processability.

[0275] The peels measured initially and after aging at 23° C. and 55° C. are determined on the laminate corresponding to each of the 2 coating temperatures of 130° C. and 145° C., by repeating the protocol A3 above.

[0276] The results are reported in Table 3.

[0277] While peel values greater than 1 N are already quite acceptable, these results show that good peels values, globally greater than about 1.5 N, are obtained, both initially and after 2 or 3 weeks storage at 23° C., for the laminate A4 comprising the HMA of Example 1. These values are just as good as those of the laminate A4 comprising the reference SBC based HMA of Example A. These levels are also obtained together with an adequate sprayability (or processability) and, most advantageously, they are achieved at coating temperatures of 130° C. and 145° C., which are well below the coating temperature of 155° C. required for Example A.

[0278] As to the peels obtained after storage at a temperature of 55° C., most of the results are still greater than about 1 N. These values are to be construed as an indicator of the HMA ability to withstand extended storage over time and under variable storage temperatures. On the whole, the peel values for the HMA of Example 1 are quite comparable with those for the reference SBC based HMA of Example A, taking also into account the much lower coating temperatures of 130° C. and 145° C., with respect to the 155° C. coating temperature for Example A.

[0279] 4. Shear Test on a Laminate A6:

[0280] A laminate A6 is prepared by repeating the protocol A6.1 of example A, except that: [0281] the coating composition is replaced by the composition of example 1; and [0282] the coating temperature of 155° C. is replaced by a coating temperature of 130° C.

[0283] The time after which the assembly fails, corresponding to the shear after 24 hours at ambient temperature, was found to be equal to 7 hours and 34 minutes, corresponding to a far better shear value with respect to the laminate A6 comprising the HMA of Example A.

[0284] 5. Peel Measured Initially and after Aging at 23° C. and at 55° C., for Laminate A7:

[0285] A laminate A7 is prepared by repeating the protocol A7 of example A, except that: [0286] the coating composition is replaced by the composition of example 1; and [0287] the coating temperature of 155° C. is replaced by a coating temperature of 130° C.

[0288] The initial peel is reported in Newton in Table 4.

[0289] The peel after storage of, respectively, 4 weeks at 23° C. and 4 weeks at 55° C. are converted into the relative value of variation of peel versus the initial peel and expressed in % in Table 4.

EXAMPLES 2 AND 3 (ACCORDING TO THE INVENTION)

[0290] Peel Measured Initially and after Aging at 23° C. and at 55° C., for Laminate A7:

[0291] A laminate A7 is prepared by repeating example 1 point 5 with the compositions of examples 2 and 3 shown in table 1.

[0292] The initial peel is reported in Newton in Table 4.

[0293] The peel after storage of, respectively, 1 week at 55° C., 2 weeks at 55° C. and 4 weeks at 55° C. are converted into the relative value of variation of peel versus the initial peel and expressed in % in Table 4.

[0294] The relative loss of peel after aging (versus the initial peel) which is observed is quite comparable to the reference SBC based HMA of Example A.

EXAMPLE 4 (COMPARATIVE)

[0295] Peel Measured Initially and after Aging at 23° C. and at 55° C., for Laminate A7

[0296] A laminate A7 is prepared by repeating example 1 point 5 with the composition of example 4 shown in table 1.

[0297] The initial peel is reported in Newton in Table 4. This peel is about half of the initial peel observed for the examples 2 and 3.

[0298] The peel after storage of, respectively, 4 weeks at 23° C., 1 week at 55° C., 2 weeks at 55° C. and 4 weeks at 55° C. are converted into the relative value of variation of peel versus the initial peel and expressed in % in Table 4.

[0299] The relative loss of peel after aging (versus the initial peel) which is observed is significantly much more important than for the HMA of examples 1, 2 and 3 according to the invention.

TABLE-US-00001 TABLE 1 HMA content in ingredient (in % weight) Exam- Exam- ple Exam- Exam- Exam- ple A ple ple ple 4 Ingredients (ref.) 1 2 3 (comp.) KRATON ® D1152 18.6 — — — — (A1) Vistamaxx ™ 8380 — 30.5 30.5 30.5 30.5 (A2) Vistamaxx ™ 8880 — 15.0 15.0 15.0 15.0 (B) ESCOREZ ® 5400 28.7 — — — — (B) ESCOREZ ® 5600 28.7 — — 17.0 39.0 (B) Sukorez ® NX700 — 34.0 — — — (B) Eastotac ® H100W — — 34.0 17.0 — Nyflex ® 223* 23.5 — — — 15.0 (C) Indopol ® H100 — 20 20 20 — (D) Irganox ® 1010 0.5 0.5 0.5 0.5 0.5 Brookfield 5,480 3,975 4,075 4,042 3,145 viscosity at 135° C. (mPa.s) *naphtenic oil

TABLE-US-00002 TABLE 2 Peel measured initially and after aging at 23° C. and 55° C. for laminates A2 obtained through Summit ™ coating equipement Example A (ref.) Example 1 Coating temperature 155° C. 130° C. 145° C. of the laminate Processability adequate adequate adequate Initial peel (N) 2.49 2.28 2.12 Peel after 2 weeks 2.06 2.39 2.66 at 23° C. (N) Peel after 4 weeks 2.94 2.13 2.5 at 23° C. (N) Peel after 2 weeks 1.45 1.99 2.27 at 55° C. (N) Peel after 4 weeks 1.41 1.72 2.04 at 55° C. (N)

TABLE-US-00003 TABLE 3 Peel measured initially and after aging at 23° C. and 55° C. for laminates A4 obtained through Signature ™ coating equipement Example A (ref.) Example 1 Coating temperature 155° C. 130° C. 145° C. of the laminate Processability adequate adequate adequate Initial peel (N) 1.53 1.62 1.44 Peel after 2 weeks 1.85 1.71 1.33 at 23° C. (N) Peel after 4 weeks 1.67 2.13 2.5 at 23° C. (N) Peel after 2 weeks 1.21 1.99 2.27 at 55° C. (N) Peel after 4 weeks 1.16 1.72 2.04 at 55° C. (N)

TABLE-US-00004 TABLE 4 Peel measured initially and after aging at 23° C. and 55° C. for laminates A7 obtained through Summit ™ coating equipement Example Example 4 A Example Example Example (compar- (ref.) 1 2 3 ative) Coating 155° C. 130° C. 130° C. 130° C. 130° C. temperature of the laminate (° C.) Processability adequate adequate adequate adequate adequate Initial peel (N) 1.35 1.05 1.35 1.68 0.78 Peel after N.T.*  +8% N.T.* N.T.* −59% 4 weeks at 23° C. (%) Peel after 1 −24% N.T.* −23% −26% −48% week at 55° C. (%) Peel after 2 −32% N.T.* −29% −33% −53% weeks at 55° C. (%) Peel after 4 −37% −39% −30% −41% −58% weeks at 55° C. (%) N.T.* = Not Tested