JPH03199283A - Hot-melt adhesive for polyolefin - Google Patents

Abstract

PURPOSE:To provide the subject adhesive composed of a specific graft copolymer containing a polyolefin (copolymer) as a backbone polymer and suitable for the bonding of a polyolefin such as PE or PP and other material. CONSTITUTION:The objective adhesive is composed of a graft copolymer containing a polyolefin or a polyolefin copolymer as a backbone polymer and a polymer having a number-average molecular weight of >=2,000 and a Tg of >=20 deg.C as a branched polymer. Example of preferable graft copolymer is the one composed of (A) 30-90wt.% of ethylene, (B) 5-50wt.% of a macromonomer having (meth)acryloyl group at one end of the molecule, a number-average molecular weight of 2,000-30,000 and a Tg of >=20 deg.C and (C) 0-40wt.% of other radically polymerizable monomer and containing <=15wt.% of an alkyl acrylate unit having 2-14C alkyl group.

Description

Detailed Description of the Invention (a) Object of the Invention [Field of Industrial Application] The present invention relates to a hot melt adhesive suitable for adhering polyolefins such as polyethylene and polypropylene to other materials.

[Conventional technology]

Polyolefins such as polyethylene and polypropylene are
Since it is a difficult-to-adhesive resin, the following adhesives are generally known as suitable adhesives for adhering them.

That is, resins such as polyethylene, ethylene-vinyl acetate copolymer (known as EVA in boat fishing), or chlorinated polypropylene are used as adhesives, or the above resins are combined with rosin, polyterpene, or petroleum. Add a tackifier such as resin or coumaron indene resin,
Furthermore, adhesives such as Mi Hakuboku are known, in which viscosity modifiers such as paraffin wax and microcrystalline wax are added as necessary.

However, although the above adhesives have good adhesion between polyolefins, there is a problem in that when adhering polyolefins to other resins, the adhesive strength to other resins is poor.

The present invention aimed to solve the above-mentioned problems existing in conventional adhesives for polyolefins.

(D) Structure of the Invention [Means for Solving the Problems] As a result of intensive studies to solve the above problems, the present inventors have discovered that ethylene and a graft copolymer obtained by radical copolymerization of a macromonomer having a (meth)acryloyl group at one end, which exhibits good compatibility with the polyolefin and the polymer skeleton of the macromonomer. The present inventors have discovered that this is extremely effective for adhesion with resins other than polyolefins, and have completed the present invention.

That is, the present invention uses a polyolefin or a polyolefin copolymer as a backbone polymer, and has a number average molecular weight of 2.
．． 000 or more and Tg is 20'C or more as a technical polymer.
(b) has a (meth)acryloyl group at one end of the molecule,
Number average molecular weight is 2.000-30,000 and Tg is 20
It consists of a graft copolymer obtained by radical copolymerization of a macromonomer and (c) other radically polymerizable monomers under high pressure, and the ratio of each of the above components in the graft copolymer is as follows: (a): 30-90% by weight
, (b): 5 to 50% by weight and (c) 20 to 40% by weight, and for polyolefins in which the proportion of acrylic acid alkyl ester units in which the alkyl group has 2 to 14 carbon atoms is 15% by weight or less It is truly a melt adhesive.

The present invention will be explained in more detail below.

The ratio of units derived from ethylene (hereinafter referred to as ethylene units) which are the constituent units of the backbone polymer of the graft copolymer in the present invention is 30 to 30, based on the total amount of all units constituting the graft copolymer. If the proportion of ethylene units is less than 30% by weight, the adhesion to the polyolefin of the adherend will be poor, while if it exceeds 90% by weight, the adhesion to resins other than polyolefin will be poor.

Preferably it is 40 to 70% by weight.

The ratio of units derived from macromonomers (hereinafter referred to as macromonomer units) in the graft copolymer is 5 to 5.
It is 0% by weight, more preferably 10 to 40% by weight. If the proportion of macro-septamer units is less than 5% by weight, the proportion of technical polymer in the graft copolymer will be too small, resulting in poor adhesion with resins other than polyolefins, while if it exceeds 50% by weight, it will be relatively difficult to adhere to ethylene. The amount of units is small and adhesion to polyolefins is impaired.

The macromonomer used in the present invention is a high molecular weight monomer having a number average molecular weight of 2,000 to 30,000 and a (meth)acryloyl group at one end of the molecule, and the polymer portion thereof Tg is 20°C or higher. If the number average molecular weight of the macromonomer is less than 2□000, the molecular chain length of the technical polymer of the graft copolymer will be too short, resulting in poor adhesive strength to resins other than polyolefin used as an adherend; ,000, the radical copolymerizability with comonomers such as ethylene is poor;
It becomes difficult to introduce the desired amount of macromonomer into the graft copolymer. A more preferable number average molecular weight is 5.
000 to 20,000. In addition, the Tg of the polymer skeleton of the macromonomer needs to be 20° C. or higher from the viewpoint of the rigidity of the branch polymer of the graft copolymer. The monomers that make up the polymer skeleton of the macromonomer are:
Styrene monomers such as styrene, α-methylstyrene, chlorstyrene, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, Examples include (meth)acrylates such as lauryl methacrylate, stearyl methacrylate, and cyclohexyl methacrylate; vinyl esters such as vinyl acetate and vinyl propionate; and unsaturated nitrile compounds such as acrylonitrile and methacrylate. Also, the number of carbon atoms in the alkyl group is 2
~14 acrylic acid alkyl ester etc. Tg is 2o''
Monomers that give a polymer with a lower C than C can also be used together with the above monomers within a range where the Tg of the copolymer does not become lower than 20°C. More preferable macromonomers are macromonomers whose polymer skeleton has a Tg of 50° C. or higher, and specifically, polystyrene-type macromonomers, polymethyl methacrylate-type macromonomers, copoly(acrylonitrile/styrene)-type macromonomers, etc. Can be mentioned.

Next, a method for producing the macromonomer will be explained.

A macromonomer with a polystyrene skeleton, i.e.
A polystyrene type macromonomer can be synthesized by an anion living polymerization termination method or an anion living polymerization initiation method. Specifically, styrene is converted into anion type polystyrene of a desired molecular weight by anion living polymerization, and the polystyrene and J styrene oxide are reacted. A method (Mi
lkovich method) etc.

A method for producing a polymethyl methacrylate type macromonomer having a polymethyl methacrylate skeleton as a backbone is to radically polymerize a methyl methacrylate monomer in the presence of a chain transfer agent containing a carboxyl group to form one end of the methyl methacrylate monomer. There is a method of synthesizing a polymer having a carboxyl group and then reacting the carboxyl group with glycidyl methacrylate to form a macromonomer (Japanese Unexamined Patent Publication No. 63101462, etc.).

A method of synthesizing a polymer having a hydroxyl group at one end using mercaptoethanol as a chain transfer agent, converting the hydroxyl group to isocyanate with tolylene diisocyanate, and converting it into a macromonomer with 2-hydroxymethacrylate, etc. Japanese Patent No. 3689593) can also be used.

In addition, commercially available macromonomers may be used, such as polymethyl methacrylate type macromonomer (AA-6 manufactured by Toa Daisoko Chemical Industry Co., Ltd.) having a number average molecular weight of 6.000, polystyrene type macromonomer having a number average molecular weight of 6.000, etc. Monomer (same as above, AS-6), styrene with number average molecular weight 6,000
Acrylonitrile copolymer type macromonomer (same as above, A
N-6) and SARTOMER number average molecular weight 13
,000 polystyrene-type macromonomers (cHEM
LINK 4,500) etc.

In addition to the above-mentioned ethylene units and macromonomer units, the graft copolymer may contain other radically polymerizable monomer units up to 50% by weight of the total structural units. As such radically polymerizable monomers, for example, 5% by weight or less of carboxyl group-containing monomers such as acrylic acid, methacrylic acid, maleic acid (anhydride), itaconic acid, etc. are used for the purpose of improving adhesion to the adherend. In addition, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (
(meth)acrylic acid alkyl esters such as stearyl meth)acrylate; styrene and its derivatives; hydroxyethyl (meth)acrylate, hydroxypropyl (
Hydroxyalkyl (meth)acrylates such as meth)acrylate; Glycidyl group-containing monomers such as glycidyl acrylate and glycidyl methacrylate; Amide compounds such as acrylamide, methacrylamide, and N-methylolacrylamide; Containers such as acrylonitrile, vinylpyridine, and vinylpyrrolidone Examples include N compounds, polyalkylene glycol mono(meth)acrylates such as polyethylene glycol monoacrylate, and polypropylene glycol monomethacrylate. These can be used alone or in combination of two or more.

Among the above radically polymerizable monomers, the content of acrylic acid alkyl ester monomer units whose alkyl group has 2 to 14 carbon atoms, which imparts adhesiveness to the polymer, is 15% by weight in the graft copolymer. It is as follows. If the proportion of such monomer units exceeds 15% by weight, the non-tacky physical properties required for hot melt adhesives at room temperature will be impaired.

The graft copolymer in the present invention is produced by high-pressure radical polymerization. Based on the total amount of all monomers,
Using a radical polymerization initiator in an amount of 0.001 to 1% by weight, a polymerization pressure of 500 to 4,000 kg/cIiY, preferably 1.000 to 3,500 kg/CrA, and a reaction temperature of 50 to 400"C1, preferably 100 The monomers may be contacted and polymerized simultaneously or in stages at ~350°C in the presence of a chain transfer agent and optionally an auxiliary agent in a tank type and/or front type reactor. can.

As the radical polymerization initiator, a radical polymerization initiator such as an organic peroxide, an azo initiator, or an amine oxide compound can be used, and as a chain transfer agent, hydrogen, propylene, butene, etc. can be used. C1-28 or higher saturated aliphatic hydrocarbons and halogenated substituted hydrocarbons, such as methane, ethane, propane, butane, isobutane, n-hexane,
Compounds such as n-heptane, cycloparaffins, chloroform and carbon tetrachloride, saturated aliphatic carbonyl compounds of C1 to C28 or higher, such as CO, acetone, methyl ethyl ketone, and aromatic compounds such as toluene, xylene, are mentioned.

Next, modes of use of the hot melt adhesive of the present invention made of the above-mentioned graft copolymer will be explained.

As mentioned above, the hot melt adhesive of the present invention can be preferably applied to bonding an adherend made of polyolefin and an adherend made of a resin other than polyolefin. Chain low density polyethylene, ultra low density polyethylene, EVA.

Ionomer resins, copolymers of ethylene and α, β-unsaturated carboxylic acids or derivatives thereof such as ethylene-ethyl acrylate copolymers, ethylene-vinyl alcohol copolymers, polypropylene, chlorinated polypropylene, ethylene propylene rubber, Examples of resins other than polyolefins include polystyrene, polyphenylene ether, polymethyl methacrylate, and ABS.
Examples include resins, polyvinyl chloride, polyamides, polyesters, and polycarbonates.

The graft copolymer in the hot melt adhesive is selected and used depending on the type of adherend so that the branch polymer of the graft copolymer and the resin to be bonded to the polyolefin have good compatibility.

Specifically, when the resin that adheres to polyolefin is polystyrene or polyphenylene ether, a graft copolymer consisting of a polystyrene-type macromonomer is used; In some cases, graft copolymers consisting of polymethyl methacrylate type macromonomers and copoly(acrylonitrile/styrene) type macromonomers are preferably used.

In addition, the hot melt adhesive of the present invention may contain a tackifier, a filler plasticizer, a viscosity modifier, other thermoplastic resins, etc. in addition to the above-mentioned graft copolymer.

(C) Effects of the Invention The hot melt adhesive of the present invention has a trunk polymer mainly composed of ethylene units and highly compatible with polyolefin, and a solubility parameter different from the trunk polymer (-SP for boat fishing).
Since the main component is a graft copolymer consisting of a branched polymer that has a high compatibility with other resins, it is possible to combine a polyolefin with another resin that is compatible with the branched polymer to achieve high strength. Can be glued. Specifically, it is possible to firmly bond polyolefin and thermoplastic resin such as polyvinyl chloride, polystyrene, methacrylic resin, ABS resin or polyphenylene ether, or metal such as aluminum or iron.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples. In addition, all parts on each side mean parts by weight.

[Examples 1 to 5] After a metal autoclave with an internal volume of 3.81 cm and equipped with a stirrer was sufficiently purged with nitrogen and ethylene, ethylene, acrylic acid alkyl ester, and chain transfer agent n- Hexane and a macromonomer were charged, di-t-butyl peroxide was added as a polymerization initiator, the polymerization pressure was 1.600 kg/c+fl, and the polymerization temperature was 17.
Polymerization was carried out at 0° C. for 1 hour.

A part of the produced polymer was dissolved in heated carbon tetrachloride, reprecipitated by pouring it into a large amount of methyl ethyl ketone, and further washed and purified with methyl ethyl ketone, then heated at 70'C.
It was vacuum dried overnight.

The purified polymer was subjected to C-NMR analysis, infrared spectroscopic analysis, and elemental analysis to confirm the composition of the graft copolymer.

"Analysis by C-NMR was carried out using a solution of the polymer in orthodichlorobenzene at 130°C and a resonance frequency of lOOMH.
I went with 2. The copolymer composition was determined mainly by the integrated intensity ratio of resonance signals in the C-NMR spectrum, and the reliability of the obtained copolymer composition was confirmed by elemental analysis values.

In Example 1, the C-NMR spectrum shows 145 ppm and 41.5 ppm derived from polystyrene units.
m and each signal of 42.5 to 47 ppm; a signal of 10 to 40 ppm derived from polyethylene units was observed, and the copolymer composition calculated based on the integrated intensity of the above signals was 83.6% by weight of polyethylene units and macromonomer. The unit is 16.4% by weight, and the elemental analysis results of the graft copolymer show that carbon is 86.3% by weight and hydrogen is 1% by weight.
It was 3.7% overlapping.

The melt index and density of the obtained graft copolymer were measured by the methods specified in JIS K6760 and JIS 7112.

The adhesion test was conducted according to the test method shown below.

(a) As a test piece for tensile shear strength, a test piece manufactured by Nippon Test Panel ■ (thickness 2 mm x width 25+ am) was used.
After heating and melting the graft copolymer at 0 to 160'C to form an adhesive layer of 0.1 mm thick on a polyethylene adherend using a heated bar coater, Another adherend was placed so that the bonding area was 25 mm x 25 mm, and a pressure of about 100 g/ci was further applied to bond the adherend.

After conditioning for 24 hours in an atmosphere of 25° C. and 165% RH, measurements were taken at a tensile rate of 50 IIlffI/min.

(b) 180° peel strength Adhesion was performed in the same manner as in (a) above, except that the adherend made of polyethylene material was a polyethylene film with a thickness of 100 μm, and after further conditioning in the same manner, a tensile speed of 300 mm/min was applied. It was measured.

Note that the above adhesive property measurement results are also listed in Table 1.

[Comparative Examples 1 to 2] Using a commercially available EVA-based true melt adhesive with a vinyl acetate content of 28% (melt flow index: 6 g/10 minutes, density: 0.95), polyethylene and polystyrene (Comparative Example 1) and polyethylene and polymethyl methacrylate (Comparative Example 2) were adhered in the same manner as each side above,
The results of evaluating the adhesive properties were as follows.

Tensile shear strength Peel strength comparison example 1 16.5 (Kg/cffl)
1.8 (Kg/inch) Comparative Example 2 15.3 (K
g/c+11) 1.2 (Kg/inch) [Example 6] Using the graft copolymer of Example 5, polyethylene and aluminum were bonded by the same method as for each side above, and the adhesive properties were evaluated. . As a result, the tensile shear strength is 6
8.0 (K g /c++1), and the peel strength is 5
．． 5 (Kg/(nf)).

Claims (1)

[Claims] 1. Polyolefin or polyolefin copolymer is used as the backbone polymer, the number average molecular weight is 2,000 or more, and T
A hot melt adhesive for polyolefins comprising a graft copolymer having a branch polymer having g of 20° C. or higher. 2, (a) ethylene, (b) has a (meth)acryloyl group at one end of the molecule,
Number average molecular weight is 2,000-30,000 and Tg is 20
It consists of a graft copolymer obtained by radical copolymerization of a macromonomer and (c) other radically polymerizable monomers under high pressure, and the ratio of each component in the graft copolymer is as follows: (a
): 30 to 90% by weight, (b): 5 to 50% by weight, and (c): 0 to 40% by weight, and the proportion of acrylic acid alkyl ester units whose alkyl group has 2 to 14 carbon atoms is 15 A hot melt adhesive for polyolefins that is less than % by weight.