AU619276B2 - Hot-melt adhesive composition - Google Patents

Description

|A U S T R A L I A AUSTRALIA PATENTS ACT 6 1 COMPLETE SPECIFICATION

ORIGINAL

(FOR OFFICE USE) Class Int Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: S Priority: S Related Art: -4 Name of Applicant(s): UB.E .N DUSTR IES,.LTD.

Address of Applicant(s): 1 2 32, Nishi-honmachi 1-chome, Ube-shi, Yamaguchi, Japan SActual inventor(s) I.wa.o Tsu.u.tan.i. an.d.. T .ak fumi.e. .Man Address for Service: PATENT ATTORNEY SERVICES 26 Ellingworth Parade, Box Hill, Victoria 3128 Complete specification for the invention entitled: HOTt-MELT ADHESIVE COMPOSITION The following statement is a full description of this invention, including the best method of performing it known to

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HOT-MELT ADHESIVE COMPOSITION Background of the Invention and Related Art Statement The present invention relates to a hot-melt adhesive composition comprising an amorphous propylene-ethylene random copolymer or an amorphous propylene-butene-1 random copolymer. More particularly, the present invention relates to a hot-melt adhesive composition having high adhesion, excellent low-temperature resistance and good fluidity and enabling easy adhesion to paper, wood, plastics, stone, a o° 10 gypsum, concrete, metals, etc.

o 0 0 As a hot-melt adhesive for polyethylene or o 0 polypropylene film, there have conventionally been used 0 those composed mainly of a polypropylene. As a low- S o 0 o viscosity hot-melt adhesives, in particular, there are used 15 those composed mainly of an amorphous atactic polypropylene.

The amorphous atactic polypropylene is obtained mostly as a by-product in the production of isotactic polypropylene and has been used because of its low cost. However, 'he atactic polypropylene is entirely or mainly composec of propylene and has poor low-temperature properties when it is I a by-product in the production of homopolymer or random copolymer, and is non-uniform in composition and accordingly in quality when it is a by-product in the production of block copolymer.

Further, being a by-product, the atactic polypropylene differs in viscosity, softening point, hardness, etc.

depending upon the properties of the isotactic polypropylene produced as an intended product; therefore, the production of an atactic polypropylene having a desired melt viscosity has been difficult. Furthermore, in the atactic polypropylene there remain the residue of the catalyst used, etc. and, because a solvent is used in the separation of isotactic polypropylene from atactic polypropylene, there also remains the solvent.

r t Thus, the hot-melt adhesive composed mainly of an 0 I0 atactic polypropylene having the above drawbacks has caused t~oe peeling at low temperatures, has had an odor and a fear of inflammation, and has been difficult to control its softening point, melt viscosity, etc.

Ott Moreover, as the activity of catalyst for polypropylene S production has been increased, the amount of atactic

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polypropylene produced as a by-product has decreased; therefore, the production of a hot-melt adhesive utilizing an atactic polypropylene as a by-product in the production *00* of isotactic polypropylene is believed to come to an end sooner or later.

Object and Summary of the Invention The present inventors made research in order to solve the above problems and to develop a high quality hot-melt adhesive and consequently have completed the present invention.

The present invention is intended to provide a hot-melt adhesive which retains the heat resistance possessed by convention hot-melt adhesives, which causes peeling or no reduction in strength at low temperatures, which gives no odor and no fear of inflammation, and which has consistent qualities in softening point, melt viscosity, etc.

According to the present invention there is provided a hot-melt adhesive composition comprising: 30-100% by weight of an amorphous propylene-ethylene random copolymer having an ethylene content of 8-30% by weight, a number-average molecular weight of 1,000-20,000, and a a o.o n-heptane insoluble of 15% by weight or less, and giving no endothermic peak by melt of crystalline when subjected to S temperature elevation by differential scanning calorimeter, 0-70% by weight of a tackifier, and 0-70% by weight of a resin.

The present invention also provides a hot-melt adhesive composition comprising: or *mro- Sa 30, by weight of an amorphous propylene-butee -1 random copolymer having a butene-1 content of 10-60% by weight, a number-average molecular weight of 1,000-20,000, a tensile break elongation of 200% or more, a ring and ball softening point of 120"C or less, a n-heptane insoluble of 20% or less and an open time of 60 seconds or more, ~r r.rore- 30% by weight of a tackifir, and or mrore.

15% by weight 4 of a resin.

The hot-melt adhesive of the present invention uses, as a main component, an amorphous propylene copolymer produced so as to meet intended purposes. Since the amorphous propylene 7 i-i copolymer is a pr iene-ethyleneor a propylene-butene-1 copolymer, the hot-melt adhesive of the present invention retains the heat resistance of polypropylene and yet has excellent low-temperature properties. Further, the 3a hot-melt adhesive of the present invention can consistently have desired properties because the main component is not a by-product obtained in the production of crystalline isotactic polypropylene.

Detailed Description The amorphous polypropylene-ethylene random or amorphous propylene-butene-1 random copolymer (hereinafter referred to simply as the random copolymer) used in the present invention can be produced by copolymerizing a mixture of liquefied propylene and liquefied ethylene or t liquefied butene-1 in the presence of hydrogen using, for example, an titanium-on-magnesium chloride catalyst and 0. triethylaluminum. The thus produced random copolymer is t, amorphous, has an ethylene content of 8-30% by weight (when it is an ethylene copolymer) or a butene-1 content of 10-60% by weight (when it is a butene-1 copolymer), and has a number-average molecular weight of 1,000-20,000. The random copolymer has consistent properties softening point, melt viscosity) 'falling in certain ranges, as compared with the atactic polypropylene obtained as a by-product in the production of isotactic polypropylene, and accordingly can be made into an adhesive of consistent quality. Further, the random copolymer can be obtained so that its softening point and melt viscosity are in desired ranges, by appropriately selecting the ratio of propylene and ethylene or butene-1 to be copolymerized and the molecular weight of the copolymer to be obtained. Furthermore, the random copolymer gives not fear of inflammation or no odor because no solvent is used in its production.

The random copolymer of the present invention is controlled so as to have a number-average molecular weight of 1,000-20,000 and an ethylene content of 8-30% by weight or a butene-1 content of 10-60% by weight. When the numberaverage molecular weight is lower than 1,000, the resulting random copolymer has a low cohesion and gives no sufficient adhesion strength. When the number-average molecular weight is higher than 20,000, the resulting random copolymer has a 0tt# ~high melt viscosity and gives operational problems such as 00 01 S• difficulty in mixing with other compounding agents due to the viscosity difference between the random copolymer and other compounding agents and non-uniform coating due to 1.1 insufficient fluidity. When the ethylene content is lower than 8% by weight, the resulting random copolymer has poor low-temperature properties and has poor compatibility with ethylenic resins. When the ethylene content is more than by weight, the resulting random copolymer is soft at normal temperature, has a low softening point, accordingly has a low cohesion when made into an adhesive, and cannot be used for high-temperature applications requiring heat resistance. When the butene-1 content is less than 10% by weight, the resulting random copolymer has a softening point

A.

ii >1

I

*1 iS o .higher than 120 0 C and, when the butene-1 content is more than 60% by weight, the random copolymer has an extremely low softening point and is unsuited as a material for hotmelt adhesives.

It is preferable that the propylene-ethylene random copolymer be amorphous in such an extent as to give no endothermic peak by melt of crystalline when subjected to temperature elevation by a differential scanning colorimeter and also to give a n-heptane insoluble of 15% or less when measured by a Soxhlet's extractor. A crystalline propyleneethylene random copolymer is not preferable because, when made into an adhesive, it gives various cohesion or various ,t I

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I Il ii r peeling modes depending upon the cooling rate after coating and because it solidifies quickly after coating and accordingly its open time cannot be taken long.

Meanwhile, the properties of the propylene-butene-1 random copolymer vary depending upon the randomness of the copolymer even if its number-average molecular weight and butene-1 content are in the above specified ranges.

2Q Preferably, the propylene-butene-1 random copolymer used in the present invention has a tensile break elongation of 200% S or more, a ring and ball softening point of 120 0 C or less and a n-heptane insoluble of 20% or less. More preferably, the random copolymer further has an open time of at least seconds.

When the tensile break elongation is less than 200%, the resulting random copolymer has a small cohesion and accordingly has a small strength when cohesive peeling occurs, which is undesirable. Such a random copolymer is unsuited for use particularly in disposable diaper, etc.

requiring a sufficient cohesion at the time of peeling.

When the softening point is higher than 120 0 C, the coating temperature is also higher than 120 0 C and consequently the adherend having a melting point of 120 0 C or less, such as low density polyethylene (LDPE) film, linear low density polyethylene (LLDPE) film or the like is melted by coating, Ta which is undesirable. When the n-heptane insoluble is ,0 higher than 20%, it implies that the random copolymer has a 4 fairly high crystallinity; this brings about quick solidification after coating and consequently a short open time, different cohesion or peeling modes depending upon the t a ,i cooling rate after coating, and volume contraction after coating, all of which are undesirable. When the open time is less than 60 seconds, the solidification time of the resulting adhesive is short and accordingly the adherend must be press-bonded in a short time after coating of the 1 adhesive, which is undesirable from the operational standpoint. The use of such a random copolymer is Srestricted particularly in, for example, a continuous production line wherein several parts are adhered or the .production speed is altered.

The random copolymer of the present invention has the above mentioned properties. It can be produced so as to have these properties or can be appropriately selected from among commercially available copolymers having said properties.

In the present invention, the random copolymer can be used as it is. But when its adhesion to adherend is poor, it can be used by incorporating thereinto a tackifier and/or a resin to increase the adhesivity, to improve the compatibility with adherend, to change the viscosity when melt-coated, or to adjust the cohesion. Further, the random o o t copolymer may be used after modification with an acid such goat as maleic anhydride or the like.

1* 5 When a tackifier is incorporated, the proportion of the random copolymer in the final adhesive is preferably 30% or more. When the proportion is 30% or less, the properties of a the random copolymer are not reflected in the resulting hotmelt adhesive.

In the present invention, as the tackifier, there can be used a natural rosin gum rosin, wood rosin, tall oil rosin), a modified rosin polymerized rosin, hydrogenated rosin, maleinized), a coumarone-indene resin, a terpene resin, a petroleum resin, a phenolic resin, etc.

Also, as the resin, there can be used an ethylene-vinyl .acetate copolymer, an ethylene-acrylic acid copolymer, an ethylene-ethyl acrylate copolymer, an ethylene methyl acrylate copolymer, a styrene-ethylene-butylene-styrene block copolymer, an ethylene-propylene or ethylene-butene copolymer having a molecular weight of 30,000 or more, a polybutene, a wax, a modified polymer or copolymer obtained by modifying the above polymer or copolymer with an acid, a metal salt of an acid, halogen or the like, etc. These tackifiers and resins can be used alone or in combination of two or more.

SThe adhesive obtained by incorporating into the random i copolymer of the present invention the above tackifier I and/or the above resin retains the properties possessed by S: o the random copolymer, such as tensile break elongation, ring 15 and ball softening point, open time and the like. In particular, the softening point of the adhesive is kept ,relatively low and its open time is about equal to that of the random copolymer; therefore, the adhesive has excellent operatability. Further, the adhesive has higher adhesion.

The adhesive can further contain a paraffinic, naphtenic or aromatic oil for the adjustment of melt viscosity and fluidity. It may furthermore contain conventionally known additives, i.e. a filler, an antioxidant, etc. As the filler, there can be used clay, talc, calcium carbonate, barium carbonate, etc. An 9 inorganic or organic fibrous reinforcing agent can also be added. As the antioxidant, there can be used dilauryl thiodipropionate, 2,6-di-tert-butyl-4-methylphenol, tetrakis[methylene-3(3,5-di-tert-butyl-4-hydroxyphenol)propionate]methane, distearyl thiodipropionate, distearyl pentaerythritol diphosphite, etc.

Even in the adhesive containing the above oil and additives, the properties of the random copolymer are not impaired; and the adhesive has excellent adhesivity and good operatability.

In the present invention, the compounding of the random I W copolymer with other polymer(s), an oil and additives can be effected by simply stirring these components in a vessel r with heating or by the use of an apparatus ordinarily used 0o o 0 0 0 0* 15 in polymer mixing, such as rolls, Banbury mixer, kneader, extruder or the like.

Being heat-meltable, the adhesive of the present invention can be used by molding into various shapes such as block, pellets, string, film and the like.

oa The adhesive of the present invention can be applied according to various methods such as a method wherein an adhesive is applied in a molten state to each of two 0 adherends using an applicator for ordinary hot-melt adhesives and the two adherends are adhered to each other, a method wherein an adhesive is applied to one adherend, other adherend is laied thereonto, and they are heated, and a method wherein an film adhesive is applied to sandwiching between adherends and heating and pressing by a laminator.

As the adherend to which the adhesive of the present invention can be applied, there can be mentioned paper, cloth, wood, synthetic resins polyethylene, polypropylene, polyvinyl chloride), gypsum, concrete, stone, metals, etc.

Particularly preferable examples of the application of the present adhesive include the application to disposable paper diaper for the adhesion between the outermost layer made of a waterproof polyethylene film and the 44.4 inner layer made of a polypropylene or polyethylene terephtalate unwoven cloth.

4,44 The adhesive of the present invention can also be applied to a moisture- and water-repellent paper obtained by laminating papers and/or paper boards with a hot-melt adhesive and having a sandwich structure, as well as to a moisture- and water-repellent paper obtained by coating one side of papers and/or paper boards with a hot-melt adhesive.

The adhesive of the present invention can also be applied as a sealing agent to fill the gaps between the two same or different substances made of the above mentioned materials.

The properties used in the present invention were measured according to the following test methods.

11 1. Number-average molecular weight Measured at 135 0 C in orthodichlorobenzene (ODCB) according to gel permeation chromatography (GPC) by Model 150C produced by Waters Co.

2. Ethylene or butene-1 content Measured using an NMR spectrum obtained by Model FX-200 produced by Nihon Denshi.

3. Endothermic peak by melt of crystalline Measured at a temperature elevation rate of 5°C/min using a differential scanning calorimeter (DSC) produced by DuPont.

*0 4. Tensile break elongation 0, Measured at a tensile speed of 50 mm/min at 24°C .40*0 S° using a No.2 test piece in accordance with JIS K 7113.

I 15 5. Ring and ball softening point Measured in accordance with JIS K 2207.

6. n-Heptane insoluble A sample was placed in a Soxhlet's extractor containing n-heptane. The system was kept for 6 hours in a n-heptane-boiling state. Then, the sample was taken out, dried in a vacuum dryer of 60 0 C, and weighed.

n-Heptane insoluble (weight of sample after extraction weight of sample before extraction) x 100 7. Open time A polymer or adhesive heated to 190 0 C was dropped on a kraft paper fixed on a glass plate, and was made into a film of 60 pm in thickness by spreading with a bar coater heated to 190 0

C.

After each given length of time 10, 20, 3, seconds), a kraft paper of the same type was placed on the polymer or adhesive film, and immediately the two papers were bonded with a rubber roller. After 5 minutes from the lamination, the two papers were peeled from each other, and there was determined the longest time (this is defined as an open time) at which there occurred no adhesive peeling between the papers and the polymer or adhesive but there occurred cohesive peeling or paper breakage.

Examples Examples 1-3 SThree hot-melt adhesives 1, 2 and 3 were prepared by melt-mixing 60 parts by weight of an amorphous propyleneethylene random copolymer (Rextac produced by El Paso Products Co. of US) shown in Table 1, with 40 parts of a .i tackifier (Hi-Rez, an alicyclic petroleum resin produced by Mitsui Petrochemical Industries, Ltd.).

Each of these hot-melt adhesives was coated on a polyethylene terephtalate film in a thickness of 60 p.

.Thereon was placed a biaxially oriented polypropylene film.

They were pressed at 120 0 C for 10 seconds at a pressure of 3 kg/cm 2 to laminate the two films. No odor was generated during the pressing.

The laminate was cut into a long narrow rectangular shape having a width of 25 mm and measured for T-peel strength at a peeling speed of 300 mm/min.

The properties of the amorphous propylene-ethylene random copolymers used and the results of measurement of adhesion strengths of the adhesives prepared are shown in Table 1 and Table 2, respectively. In Table 2, A refers to o t

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adhesive peeling and C refers to cohesive peeling, and this 0 applies to other tables.

O O 00 9 o 0 4091 o o I I t 1'a b I A dh e s ive REB XT''A C B 2 A80 3 R U X T A C PB 5 A 8 0 Brand Name C, X 'l A C B 3 A 't)0 6, 800 Num her -averag-e M1ole Ccula r We i ghi t 7, 4100 7,30 0 Amorphous CopolIymer BEthyle ne Col t en t (W t t f tiff t I f I ft t

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II ft I f I I E ndo Lthe ra mi c Peak by Mielt of Crystalline n hep ta no I a s o I (I b I a (O N ot a ppea red No t Not appeared appeared 9.0 8.7

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11 Table 2 A d h e s i v o Amo ar phoau s c- t hy 1 rnie propylone- Co pa I y 1.11e c 1 REX [A C 1B 2 A 8 0 I tl 4 t i It,; A d h es i a n Strength (k g /25m[i) 0 C 3. 2 2 5. 0 2 RR XT TA C B3A8O 4. 5 A 4. 5 c 2. 4 C 3 BE 5A C 41.0 A 3. 7 C 4 0 *C 2. 7 1. 3~ C Comparative Example 1 An adhesive 1' was prepared in the same manner as in Example 1 except that the amorphous propylene-ethylene random copolymer was replaced by an atactic polypropylene (Vistac L produced by Chiba Fine Chemical Co.) having a propylene content of about 100%. The results are shown in Table 3. Incidentally, an odor which presumably came from the solvent used, was generated during the preparation of the adhesive and also in the adhesive.

1 Table 3 a A d h e s i v e 0 °C 0.1 A Adhesion Strength So* (kg/25mm) 2 5 "C 3.5 A 4 0 °C 2.9 A Comparative Example 2 An adhesive 2' was prepared in the same manner as in S Example 1 except that the amorphous propylene-ethylene random copolymer was replaced by Tafmer PO 180 (a product of Mitsui Petrochemical Industries, Ltd.) having an ethylene content of about 75% by weight and a propylene content of about 25% by weight. The results are shown in Table 4.

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A

7.

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i I 71 9, 4 Ta ble 4 Adhesive 2' 0 C 5.2 A Adhesion Strength 2 5 °C 4.0 C 4 0 "C 0.2 C It I It I Ir Example 4 In the same manner as in Example 1, there were prepared three hot-melt adhesives 4, 5 and 6 each comprising, as shown in Table 5, the propylene-ethylene random copolymer used in Example 1 and an ethylene-vinyl acetate [V 319 (brand name) produced by Ube Industries, Ltd.] having a melt index of 15 g/10 min and a vinyl acetate content of 19% by weight. These adhesives were measured for adhesion strength. The results are shown in Table T ablIe A di h e s i v e C o rnt p a S i t i co a R? F X 'IA C 112 A80:40 E VA :2 0 11 i I? 2i 'r1' 115: '10 b I? E XT'1 A C B3 A80: 110 F VA :20 I Rez Tl 115:4'0 6 RCXT TA C 13A8O0:40 EV A H i I? az T1 I[115 4 0 4-- 0 *i 6.- *too to 0 4 Adhes ion Strength (k g/25mm 2 5 'C /1 0 0 c 5.4 5. 2 '1.

A

A

c 5. 0 2. 1

A

A

c 3.0 91C Example Adhesives 7 and 8 were prepared by melt-mixing, at 160 0 C, 70% by weight of an amorphous propylene-butene-1 random copolymer (Rextac E-4 or E-5 produced by El paso products Co. of US) as shown in Table 6 and 30% by weight of a tackifier [Arkon P-125 (brand name), an alicyclic petroleum resin produced by Arakawa Kagaku An adhesive 9 was prepared by melt-mixing, at 180°C, by weight of the above-mentioned amorphous propylenebutene-1 random copolymer (Rextac 15% by weight of a styrene-ethylene-butylene-styrene block copolymer (Kraton G 1657X, a thermoplastic elastomer produced by Shell Chemical) and 30% by weight of a tackifier [Arkon P-125 (brand name), 5I' an alicyclic petroleum resin produced by Arakawa Kagaku Each of the adhesives 7, 8 and 9 was coated on a polypropylene unwoven cloth at 105 0 C, immediately, a LLDPE film of 20 nm in thickness was press-bonded thereonto to obtain 3 laminated test pieces X. Also, 3 laminated test pieces Y were obtained in the same manner except that the coating temperature was 150 0 C and the pressure bonding of the LLDPE was effected after the coated unwoven cloth had been allowed to stand for 30 seconds.

K Each of the above 6 test pieces was cut into a long 25 narrow rectangular shape of 25 mm in width and measured for adhesion strength in the same manner as in Example 1. Also, the condition of damage of LLDPE film was examined. The results are shown in Table 7.

T ablIe 6 A d h es ive 7 Brand Name .1,

F;:

F;

t lsF; Amorphous Copol ymer Mi olI e c u 1 a r we i ghI t B u t en e- Content (W t.% ,fensi le Bre~ak E I o n g a t i o n R inrg B Ba Il So fleni, P o in1t rn -her)tane i flso I LI I e Open Time (S ec) R[IXTAC 13-- 4 6, 700 40 250 110 RIITAC 91 000 350 110 9.8 400 4 00 jL Ta blIe 7 E xamrnp 1 e T e st p ie ce X- I- -Y Adhesive Coa ting TemperatLure Time of Standing a fter Coa t ing (Sec.) ]07 8 105 105 7 8 9fi.

151 151 150 30 3 0 Adhesion Strength (k g/25 mm) 25 'C S40 -C 3. 3. 8 .2 1 i3~ 3. 2 3.9 2 .H _3 1_ 4.1 2.8 Condition of Damage of LLDPI1 None I None I None I None I None INone iii

Claims (2)

1. A hot-melt adhesive composition comprising:

30-100% by weight of an amorphous propylene-ethylene random copolymer having an ethylene content of 8-30% by weight, a number-average molecular weight of 1,000-20,000, and a n-heptane insoluble of 15% by weight or less, and giving no endothermic peak by melt of crystalline when subjected to temperature elevation by differential scanning calorimeter, 0-70% by weight of a tackifier, and 0-70% by weight of a resin. 2. A hot-melt adhesive composition comprising: or mr\ore 30 by weightjof an amorphous propylene-butene.-l random copolymer having a butene-1 content of 10-60% by weight, oa o a number-average molecular weight of 1,000-20,000, a tensile o o$ break elongation of 200% or more, a ring and ball softening point of 120*C or less, a n-heptane insoluble of 20% or less and an open time of 60 seconds or more, or Yo 30% by weight of a tackifier, and c= rvo r-p- I5% by weight of a resin. S• 3. A hot-melt adhesive composition according to Claim 1 or 2, wherein the tackifier is a petroleum resin. 4. A hot-melt adhesive composition according to any one of Claims 1 to 3, wherein the resin is an ethylene-vinyl acetate Scopolymer. A hot-melt adhesive composition according to any one of Claims 1 to 3, wherein the resin is a styrene-ethylene-butylene- styrene block copolymer. S23 I 2- 6. A hot-melt adhesive composition substantially as herein before described in any one of the Examples. Dated this 19th day of July, 1991 PATENT ATTORNEY SERVICES Attorneys for UBE INDUSTRIES, LTD U oe o so ooo a os e oaoo 0 o Doo 0094 oo oa 0 0 9 a e* a SD fiB G o ro ?D a a o 9 e a oose oli e o ee 4 S a a a ae ee o *a o L