CN117460803A

CN117460803A - Tackifier and adhesive composition

Info

Publication number: CN117460803A
Application number: CN202280037259.6A
Authority: CN
Inventors: 岩田昂; 千叶大二郎
Original assignee: Asahi Kasei Corp
Current assignee: Asahi Kasei Corp
Priority date: 2021-07-01
Filing date: 2022-06-16
Publication date: 2024-01-26

Abstract

The purpose of the present invention is to provide a tackifier which can be suitably used as a tackifier for adhesives and which has excellent long-term storage stability when used as a tackifier for adhesives, particularly cyanoacrylate adhesives. An adhesive agent comprising a methacrylic resin having a Mw of 85000 ～ 1500000, wherein the viscosity of an ethyl cyanoacrylate solution of the methacrylic resin at 25 ℃ is eta 1, the solution is left at 60 ℃ for 48 hours, the solution is cooled to 25 ℃, and the viscosity of the cooled solution at 25 ℃ is eta 2, wherein 1.0 eta 2/eta 1 eta 5.0 is satisfied (wherein the concentration of the methacrylic resin in the solution is 20 mass%, 10 mass% or 7 mass% depending on the Mw of the methacrylic resin).

Description

Tackifier and adhesive composition

Technical Field

The present invention relates to tackifiers and adhesive compositions.

Background

In the production of a paint, an adhesive, or the like, an organic thickener is used for the purpose of adjusting the viscosity of a product to improve the workability. Among the organic tackifiers, the tackifiers using the methacrylic resin composition have high transparency and weather resistance as transparent resins, and also have excellent affinity with alkyl cyanoacrylates and the like and chemical resistance. Since the methacrylic resin composition is rapidly dissolved in a monomer while maintaining transparency, it is widely used as a tackifier for adhesives.

In adhesives, particularly cyanoacrylate adhesives, because of the high anionic polymerizability of alkyl cyanoacrylates as a main component, polymerization starts due to a small amount of weak anions such as moisture and impurities, and various materials can be firmly bonded in a short time. Therefore, the adhesive is widely used in a wide range of fields such as industrial, medical and household applications as a transient adhesive.

Due to its high polymerizability, cyanoacrylate-based adhesives are transported and stored in an environment such as a closed container, which is to some extent isolated from the outside air. However, cyanoacrylate adhesives are sometimes handled under high-temperature and high-humidity conditions depending on conditions of transportation, storage and use, and when left for a long period of time under such conditions, the viscosity of the cyanoacrylate adhesives may be increased, and thus improvement is demanded.

In addition, cyanoacrylate adhesives sometimes have a peculiar odor caused by a tackifier contained in the adhesive, and thus reduction of the odor is also demanded.

Patent document 1 discloses an acrylic tackifier which is excellent in solubility in methyl methacrylate and has a characteristic in molecular weight distribution.

Patent document 2 discloses a tackifier containing a methacrylic resin excellent in stability when exposed to 50 ℃/95% rh in methyl methacrylate.

Patent document 3 describes that a cyanoacrylate-based adhesive composition contains, as a tackifier, a polyalkyl (meth) acrylate having a weight average molecular weight of 200000 ～ 500000.

Prior art literature

Patent literature

Patent document 1: japanese patent No. 5131956.

Patent document 2: japanese patent application laid-open No. 2018-178076.

Patent document 3: japanese patent publication No. 4-15267.

Disclosure of Invention

Problems to be solved by the invention

Patent document 1 does not describe solubility in alkyl cyanoacrylate and long-term storage stability when dissolved in alkyl cyanoacrylate which is easily polymerized due to the influence of a small amount of moisture or impurities.

Patent document 2 discloses a tackifier having excellent long-term stability in methyl methacrylate by introducing a specific structure into the terminal of a resin, but it does not describe long-term stability in alkyl cyanoacrylate.

In patent document 3, various stabilizers are added to constitute a cyanoacrylate-based adhesive, and there is no description about the contribution of an acrylic tackifier itself to stabilization.

Accordingly, an object of the present invention is to provide a tackifier which can be suitably used as a tackifier for adhesives, particularly a tackifier for cyanoacrylate adhesives, and which has excellent long-term storage stability.

Means for solving the problems

As a result of intensive studies to solve the above problems, the present inventors have surprisingly found that a viscosity change rate of a thickener which is dissolved in ethyl cyanoacrylate and then left at 60 ℃ for 48 hours falls within a specific range, thereby obtaining a thickener excellent in long-term storage stability, and have completed the present invention.

Namely, the present invention is as follows.

[1] A tackifier which is a methacrylic resin tackifier having a weight average molecular weight (Mw) 85000 ～ 1500000, wherein η1 and η2 are satisfied when a viscosity (pa·s) of an ethyl cyanoacrylate solution of the methacrylic resin at 25 ℃ is defined as η1, the solution is left to stand at 60 ℃ for 48 hours, cooled to 25 ℃, and a viscosity (pa·s) of the solution at 25 ℃ after cooling is defined as η2: 1.0.ltoreq.eta.2/eta.1.ltoreq.5.0.

And, when the Mw of the methacrylic resin is 85000 or more and less than 300000, the concentration of the methacrylic resin of the solution is 20 mass%, when the Mw of the methacrylic resin is 300000 or more and less than 800000, the concentration of the methacrylic resin of the solution is 10 mass%, and when the Mw of the methacrylic resin is 800000 or more and 1500000 or less, the concentration of the methacrylic resin of the solution is 7 mass%.

[2] The tackifier according to [1], wherein the methacrylic resin contains 90 to 99.9% by mass of methyl methacrylate monomer units and 0.1 to 10% by mass of alkyl acrylate monomer units.

[3] The tackifier according to [2], wherein the alkyl group of the alkyl acrylate monomer unit has a carbon number of 4 or more.

[4] The tackifier according to [1], wherein the methacrylic resin contains 90 to 99.9 mass% of methyl methacrylate monomer units and 0.1 to 10 mass% of aromatic vinyl compound monomer units.

[5] The tackifier according to [4], wherein the methacrylic resin contains 90 to 99.8 mass% of methyl methacrylate monomer units, 0.1 to 8 mass% of aromatic vinyl compound monomer units and 0.1 to 8 mass% of acrylate monomer units.

[6] The tackifier according to [5], wherein the alkyl group of the alkyl acrylate monomer unit has a carbon number of 4 or more.

[7] The tackifier according to any one of [1] to [3], wherein the moisture content of the methacrylic resin measured by a drying method is 0.01% or more and 1% or less.

[8] The thickener according to any of [1] to [4], wherein the methacrylic resin is in the form of beads having an average particle diameter of 50 to 500. Mu.m.

[9] The thickener according to [5], wherein the mass ratio of particles having a particle diameter of 710 μm or more is 5% by mass or less relative to 100% by mass of the thickener.

[10] A cyanoacrylate-based adhesive composition comprising 1 to 30% of the tackifier according to any one of [1] to [6 ].

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a tackifier which can be suitably used as a tackifier for an adhesive, particularly a tackifier for a cyanoacrylate adhesive, can suppress an increase in viscosity of a tacky object during storage, can be cured, and can improve storage stability of a product.

Detailed Description

Hereinafter, embodiments for carrying out the present invention (hereinafter, referred to as "the present embodiment") will be described in detail, but the present invention is not limited to the following embodiments, and can be variously modified and carried out within the gist thereof.

In the present embodiment, unless otherwise specified, "methacrylic resin" refers to a resin having a weight average molecular weight (Mw) of 85000 ～ 1500000 and containing 80 mass% or more of methyl methacrylate monomer units as monomer units.

[ tackifier ]

The tackifier of the present embodiment contains at least methacrylic resin. The tackifier may contain only methacrylic resin, or may contain methacrylic resin and other resins. For the tackifier, it is preferable that the resin component is only methacrylic resin. The tackifier may be 1 kind of methacrylic resin alone or 2 or more kinds of methacrylic resins in combination. In one example, it is more preferable that the tackifier is composed of only a single methacrylic resin as the resin component.

The tackifier can be suitably used as a tackifier for adhesives, particularly a tackifier for cyanoacrylate adhesives.

< viscosity ratio >)

In this embodiment, when the viscosity (pa·s) of an ethyl cyanoacrylate solution of a methacrylic resin at 25 ℃ is assumed to be η1, the solution is left at 60 ℃ for 48 hours, cooled to 25 ℃, and the viscosity (pa·s) of the cooled solution at 25 ℃ is assumed to be η2, η1 and η2 satisfy: 1.0.ltoreq.eta.2/eta.1.ltoreq.5.0. By setting η2/η1 (hereinafter, sometimes simply referred to as "η ratio") to 1.0 or more and 5.0 or less, the viscosity and the adhesive property can be maintained even when the adhesive is left for a long period of time (for example, several months) under normal temperature conditions after the tackifier is dissolved in the alkyl cyanoacrylate.

The temperature at which the methacrylic resin is dissolved in ethyl cyanoacrylate is preferably 50℃or higher. After the methacrylic resin was dissolved, the temperature of the solution was set to 25 ℃, and the viscosity η1 was measured.

After measuring the viscosity η1 of the solution at 25 ℃, the solution was warmed to 60 ℃. Next, the solution was left at 60 ℃ for 48 hours, cooled to 25 ℃, and the viscosity η2 of the solution at 25 ℃ after cooling was measured. Here, the 48 hours at 60 ℃ means that the lapse of time after the solution was put in an oven at 60 ℃ is 48±1 hours.

As a method for adjusting the ratio of η to 1.0 or more and 5.0 or less, there is mentioned copolymerization of alkyl acrylate monomer units in a predetermined amount, copolymerization of a small amount of aromatic vinyl compound monomer units, adjustment of the water fraction of the methacrylic resin, reduction of the weight ratio of particles having a particle diameter of 710 μm or more, and acid/alkali washing to adjust the pH of the aqueous phase when the thickener is dispersed in water to 2 or more and 9 or less, and reduction of impurities in the thickener as much as possible, and the like, and it is preferable to combine a plurality of them.

The ratio of η is preferably 1.0 to 4.5, more preferably 1.0 to 4.0. When the η ratio is less than 1.0, the viscosity is lowered after dissolution, and the composition cannot function as a thickener. If the η ratio is more than 5.0, the adhesive may be cured or the strength as a cured adhesive may be deteriorated when the adhesive is stored for a long period of time such as several months or when the air temperature rises during transportation.

The concentration of the methacrylic resin in the ethyl cyanoacrylate solution is 20 mass% when the Mw of the methacrylic resin is 85000 or more and less than 300000, 10 mass% when the Mw of the methacrylic resin is 300000 or more and less than 800000, and 7 mass% when the Mw of the methacrylic resin is 800000 or more and 1500000 or less.

When methacrylic resins having different ranges of Mw are contained in the ethyl cyanoacrylate solution, the Mw of the entire methacrylic resin may be measured, and the concentration may be determined based on the Mw.

(methacrylic resin)

Preferably, the methacrylic resin contains 90 to 99.9 mass% of methyl methacrylate monomer units and 0.1 to 10 mass% of alkyl acrylate monomer units. The methacrylic resin may or may not contain a methyl methacrylate monomer unit and a monomer unit other than an alkyl acrylate monomer unit.

The alkyl acrylate monomer unit preferably has an alkyl group having 4 or more carbon atoms. As the alkyl acrylate monomer unit having an alkyl group having 4 or more carbon atoms, a monomer unit derived from an alkyl acrylate having an alkyl group having 4 to 8 carbon atoms such as n-butyl acrylate, sec-butyl acrylate, 2-ethylhexyl acrylate or the like is preferably used. From the viewpoint of reducing the odor of the cyanoacrylate solution of the methacrylic resin, the carbon number of the alkyl group of the alkyl acrylate monomer unit is preferably 4 to 8. From the viewpoints of ease of obtaining and reduction of odor upon dissolution in cyanoacrylate, n-butyl acrylate monomer units are particularly preferable.

The methacrylic resin may be composed of only methyl methacrylate monomer units and alkyl acrylate monomer units having an alkyl group having 4 or more carbon atoms, or may further contain other monomer units such as other vinyl monomer units copolymerizable with methyl methacrylate.

The other monomer unit may be a vinyl monomer copolymerizable with methyl methacrylate, and specifically, an alkyl methacrylate having an alkyl group with 2 to 18 carbon atoms; alkyl acrylate with alkyl of 1-3 carbon number; alpha, beta-unsaturated acids such as acrylic acid and methacrylic acid; unsaturated group-containing divalent carboxylic acids such as maleic acid, fumaric acid, itaconic acid, and alkyl esters thereof; aromatic vinyl compounds such as styrene, α -methylstyrene, and styrene having a substituent on the benzene ring; cyanide vinyl compounds such as acrylonitrile and methacrylonitrile; maleic anhydride, maleimide, N-substituted maleimide; esters of ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, and the like, each of which has hydroxyl groups at both ends of ethylene glycol or an oligomer thereof, which are esterified with acrylic acid or methacrylic acid; esters obtained by esterifying hydroxyl groups of 2 alcohols such as neopentyl glycol di (meth) acrylate and di (meth) acrylate with acrylic acid or methacrylic acid; esters of polyhydric alcohol derivatives such as trimethylolpropane and pentaerythritol by acrylic acid or methacrylic acid esterification; multifunctional monomers such as divinylbenzene; etc. They can be used singly or in combination of two or more. In the case of an alkyl acrylate having 1 to 3 carbon atoms in the alkyl group, the mass ratio of the monomer units derived from the alkyl acrylate having 1 to 3 carbon atoms in the alkyl group is preferably less than 0.1 mass%, and more preferably not contained, relative to 100 mass% of the total monomer units constituting the methacrylic resin, from the viewpoint of odor suppression.

From the viewpoint of suppressing the odor when dissolved (for example, when dissolved in alkyl cyanoacrylate), the mass ratio of the monomer unit derived from methyl methacrylate to 100 mass% of the methacrylic resin is preferably 90 to 99.9 mass%. More preferably 95 to 99.8% by mass, still more preferably 97 to 99.8% by mass, particularly preferably 98 to 99.8% by mass.

The mass ratio of the alkyl acrylate monomer unit to 100 mass% of the methacrylic resin is preferably 0.1 to 10 mass%. More preferably 0.2 to 5% by mass, still more preferably 0.2 to 3% by mass, and particularly preferably 0.2 to 2% by mass. If it exceeds 5% by mass, it is not preferable because a specific odor is generated by the residual alkyl acrylate monomer or impurities derived therefrom when dissolved in alkyl cyanoacrylate or the like. When the amount is less than 0.1% by mass, the effect of improving the smell obtained by copolymerizing the alkyl acrylate monomer units cannot be exerted, and thus it is not preferable.

In the present embodiment, other monomer units may be copolymerized within a range that does not impair the effects of the present invention. When considering the solubility in cyanoacrylate or the like, the odor during dissolution, or the like, the mass ratio of the monomer units derived from the other vinyl monomer copolymerizable with methyl methacrylate is preferably 0 to 20 parts by mass, more preferably 15 parts by mass or less, still more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass, based on 100 parts by mass of the total amount of methyl methacrylate and alkyl acrylate monomer units having an alkyl group of 4 or more carbon atoms.

The total mass ratio of the monomer units derived from methyl methacrylate and the alkyl acrylate monomer units having an alkyl group having 4 or more carbon atoms in 100 parts by mass of the methacrylic resin is preferably 80 parts by mass or more, more preferably 85 parts by mass or more, further preferably 90 parts by mass or more, further preferably 95 parts by mass or more, and particularly preferably 100 parts by mass.

From the viewpoint of improving the storage stability of the cyanoacrylate-based adhesive, the methacrylic resin preferably contains an aromatic vinyl compound monomer unit. The mechanism by which the storage stability of the cyanoacrylate-based adhesive can be improved by the aromatic vinyl compound monomer unit is presumably due to the incorporation of a monomer having weak electron withdrawing property and low anionic polymerizability of an aromatic group.

Preferably, the methacrylic resin contains 90 to 99.9 mass% of methyl methacrylate monomer units and 0.1 to 10 mass% of aromatic vinyl compound monomer units. In one embodiment, the aromatic vinyl compound monomer units are monomer units derived from styrene.

In one embodiment, the content of the aromatic vinyl compound monomer unit is 0.2 mass% or more, 0.3 mass% or more, 0.5 mass% or more, 1.0 mass% or more, 1.5 mass% or more, 2.0 mass% or more, 2.5 mass% or more, 3.0 mass% or more, 3.5 mass% or more, 4.0 mass% or more, 4.5 mass% or more, 5.0 mass% or more, 6.0 mass% or more, 7.0 mass% or more, 8.0 mass% or more, or 9.0 mass% or more, relative to 100 mass% of the methacrylic resin. In another embodiment, the content of the aromatic vinyl compound monomer unit is 10.0 mass% or less, 9.0 mass% or less, 8.0 mass% or less, 7.0 mass% or less, 6.0 mass% or less, 5.0 mass% or less, 4.5 mass% or less, 4.0 mass% or less, 3.5 mass% or less, 3.0 mass% or less, 2.5 mass% or less, 2.0 mass% or less, 1.5 mass% or less, or 0.5 mass% or less, based on 100 mass% of the methacrylic resin. When the amount is more than 10% by mass, the productivity is deteriorated, and a specific odor may be generated due to the residual aromatic vinyl compound monomer, which is not preferable. When the content is less than 0.1% by mass, the effect of improving storage stability cannot be obtained when the tackifier is added to a cyanoacrylate adhesive, and this is not preferable.

In one embodiment, the methacrylic resin contains 90 to 99.9 mass% of methyl methacrylate monomer units and 0.1 to 10 mass% of the total of 1 or more selected from the group consisting of alkyl acrylate monomer units and aromatic vinyl compound monomer units.

< weight average molecular weight >

The weight average molecular weight of the methacrylic resin was 85000 ～ 1500000 as determined by Gel Permeation Chromatography (GPC). If the Mw is less than 85000, the amount of the thickener used for bringing the slurry (solution in which the methacrylic resin is dissolved) to a predetermined viscosity increases, and thus the mechanical properties of the resulting adhesive or the like may be deteriorated, which is not preferable. On the other hand, from the viewpoints of solubility and characteristic stability, mw is 1500000 or less. The particularly preferable molecular weight varies depending on the viscosity and the required properties desired at the time of dissolution, and is preferably 85000 or more and less than 300000 when the viscosity is low or the dissolution rate is to be increased. On the other hand, when the viscosity is used at a relatively high viscosity or a desired viscosity is to be obtained by adding a small amount, it is preferably 300000 or more and 1500000 or less.

< moisture Rate >

The moisture content of the methacrylic resin is preferably 0.01% or more and 1% or less. If the water content is to be suppressed to be lower, there is a case where the necessity of drying for a long time arises. From the viewpoint of productivity, it is preferably 0.01% or more. On the other hand, if the content is more than 1%, the storage stability after dissolution in cyanoacrylate such as ethyl cyanoacrylate tends to be poor, and therefore, it is preferably 1% or less. More preferably, it is not less than 0.01% and not more than 0.8%, still more preferably not less than 0.02% and not more than 0.7%, and most preferably not less than 0.03% and less than 0.7%. Depending on the mode of use, the storage period of the tackifier before dissolving the tackifier of the present invention in an adhesive such as a cyanoacrylate-based adhesive may be prolonged, and the methacrylic resin absorbs moisture during this period, so that it is preferable to reduce the initial moisture of the methacrylic resin as much as possible.

The water content can be measured by the method described in examples described below, and can be measured by a drying method. The drying method is a method in which 10.0g of methacrylic resin is kept at 70℃and after a weight reduction rate of 10 seconds is 0.02% or less, the measurement is completed and the total weight reduction rate is taken as the water content.

The moisture content of the methacrylic resin (for example, the particulate or bead methacrylic resin) can be adjusted by, for example, a drying method of the slurry after polymerization or the like.

Examples of the method for drying the methacrylic resin include hot air drying in which hot air is supplied from a hot air blower, a heating fan (blow heater), or the like into a tank, vacuum drying in which the inside of the system is depressurized and then heated as needed, drum drying in which the obtained polymer is rotated in a container to disperse water, rotary drying in which the obtained polymer is dried by centrifugal force, air-flow drying in which the resin in a hot air supply pipe is dried while being dried, and a fluidized bed dryer in which the tank bottom is opened and closed after drying for a predetermined time under a specific temperature condition and then falls down to the next drying tank.

In order to set the water content within the above range, it is preferable that the slurry obtained after the suspension polymerization is finished is dried by a pneumatic dryer and/or a fluidized bed dryer. In this case, if the final moisture content is low, the processing takes time, and therefore the productivity is poor, and there are cases where problems such as poor pumping occur in the slurry transporting process.

The thickener according to this embodiment can be used for manufacturing slurry for artificial marble, paint, adhesive, and the like.

The tackifier of the present embodiment is particularly preferably used for cyanoacrylate-based adhesives. Here, as the cyanoacrylate-based adhesive, an adhesive containing an alkyl cyanoacrylate as a main component is preferable (for example, the mass ratio of the alkyl cyanoacrylate is 50% by mass or more, more preferably 70% by mass or more with respect to 100% by mass of the adhesive).

Examples of the alkyl cyanoacrylate include cyanoacrylates having an alkyl group having 1 to 10 carbon atoms such as methyl cyanoacrylate, ethyl cyanoacrylate, propyl cyanoacrylate, isopropyl cyanoacrylate, butyl cyanoacrylate, isobutyl cyanoacrylate, octyl cyanoacrylate, and the like; ethyl methoxycyanoacrylate, ethyl ethoxycyanoacrylate, and the like. In general, ethyl cyanoacrylate is mostly used.

The ratio Mw/Mn of the weight average molecular weight Mw to the number average molecular weight Mn of the methacrylic resin measured by Gel Permeation Chromatography (GPC) is preferably 1.7 or more and 2.5 or less. From the viewpoint of ease of production, it is more preferably 1.8 or more. In addition, from the viewpoint of suppressing dissolution residual at the time of dissolution and improving solubility, it is more preferably less than 2.5, still more preferably 2.4 or less, particularly preferably 2.3 or less, and particularly preferably less than 2.3.

The weight average molecular weight and the number average molecular weight were measured by GPC. Standard methacrylic resins, which have a known monodisperse weight average molecular weight and can be obtained as reagents, and analytical gel chromatography columns, which elute from the high molecular weight component, are used in advance, and a standard curve is established based on elution time and weight average molecular weight. The molecular weight of each sample can be measured from the standard curve. Specifically, the measurement can be performed by the method described in examples described below.

The shape of the methacrylic resin is not particularly limited, but is preferably in the form of particles, flakes, beads or powder. From the viewpoint of shortening the dissolution time or reducing the unmelts, beads or powder are preferable.

< volume average particle diameter >)

In the methacrylic resin, the volume average particle diameter when used in the form of beads is preferably 50 to 500. Mu.m. The smaller the particle diameter is, the shorter the dissolution time is, and therefore, preferably 450 μm or less, and from the viewpoint of suppressing scattering of beads during the operation and from the viewpoint of reducing unmelts, preferably 50 μm or more. The volume average particle diameter is more preferably 70 to 400. Mu.m, most preferably 100 to 350. Mu.m.

In the present specification, the volume average particle diameter refers to a volume particle diameter that can be measured by a method described in examples described below.

From the viewpoint of obtaining a high solubility with respect to alkyl cyanoacrylate and the viewpoint of adjusting the ratio of η, the mass ratio of particles having a particle diameter of 710 μm or more with respect to 100 mass% of the methacrylic resin (preferably methacrylic resin beads) is preferably 5 mass% or less, more preferably 3 mass% or less, further preferably 1 mass% or less, particularly preferably 0.5 mass% or less, and particularly preferably 0.1 mass% or less. The mass ratio of particles having a particle diameter of 710 μm or more can be measured by the method described in examples described later. Examples of the method for adjusting the mass ratio of particles having a particle diameter of 710 μm or more include polymerization in which the particle diameter of the suspending agent is reduced under stable conditions.

< polymerization method >)

The methacrylic resin can be produced, for example, using a monomer constituting the methacrylic resin, a polymerization initiator, a chain transfer agent, a suspending agent, other additives, and the like.

When a radical polymerization is used as the polymerization initiator, a general radical polymerization initiator of an azo type such as di-t-butyl peroxide, lauroyl peroxide, dilauryl peroxide, t-butylperoxy 2-ethylhexanoate, a peroxide type such as 1, 1-bis (t-butylperoxy) -3, 5-trimethylcyclohexane, 1-bis (t-butylperoxy) cyclohexane, azobisisobutyronitrile, azobisisovaleronitrile, and 1, 1-azobis (1-cyclohexane carbonitrile) may be used alone or in combination of two or more. These radical initiators can also be implemented as redox system initiators in combination with suitable reducing agents.

The polymerization initiator is generally used in the range of 0.001 to 1 mass% relative to 100 mass% of the total mass of the monomers.

In the method for producing a methacrylic resin, in the case of production by a radical polymerization method, a chain transfer agent which is generally used can be used to adjust the molecular weight.

As the chain transfer agent, for example, mercaptans such as n-butylmercaptan, n-octylmercaptan, n-dodecylmercaptan, 2-ethylhexyl thioglycolate, ethylene glycol dimercaptoacetate, trimethylolpropane trimercaptate, pentaerythritol tetrakis (mercaptoacetate) and the like are preferably used.

The chain transfer agent may be used in the range of 0.001 to 1 mass% relative to 100 mass% of the total mass of the monomers. The amount of chain transfer agent depends on the desired molecular weight.

As a polymerization method of the methacrylic resin, suspension polymerization or emulsion polymerization is preferably used. Suspension polymerization provides resin beads in a particulate form, and emulsion polymerization provides resin beads in a powder form, and therefore is advantageous in terms of handling when an appropriate amount of the resin beads is dissolved as a thickener for adjusting the slurry to a desired viscosity.

Suspension polymerization takes a shorter polymerization time than emulsion polymerization, and suspension polymerization is therefore preferred.

In particular, when the suspension polymerization method is used, it is preferable to set the molecular weight distribution in the above range, and when it is required to suppress the occurrence of unmelted due to the breadth of the molecular weight distribution when dissolved in alkyl cyanoacrylate or the like at a high level and to maintain high storage stability after dissolution, it is not multistage polymerization in which the molecular weight distribution is broadened, but it is preferable to obtain it by one stage suspension polymerization. If the polymerization is a two-stage polymerization, the amount of impurities derived from the suspending agent increases, which is not preferable.

As a method for polymerizing the methacrylic resin, a method of dispersing a suspending agent having an average particle diameter of 10 to 40 μm in water and polymerizing the dispersed agent is preferably used. Among them, it is preferable to carry out the one-stage suspension polymerization by dispersing a suspending agent having an average particle diameter of 10 to 40 μm in water.

In the method for producing a methacrylic resin, it is preferable to polymerize the suspending agent dispersed in the suspension polymerization water so that the average particle diameter is 10 to 40. Mu.m. This can control the standard deviation of the volume particle diameter of the methacrylic resin (e.g., methacrylic resin beads), stabilize the polymerization behavior, reduce the heat release, and improve the productivity.

The average particle diameter of the suspending agent can be adjusted by appropriately selecting the particle diameter of the suspending agent to be used. Further, by mixing powders having different particle diameters, a suspension having an appropriate average particle diameter can be obtained.

In the method for producing a methacrylic resin, the pH of the aqueous phase is preferably adjusted to a range of 4 to 7. When the pH is within this range, the standard deviation of the particle diameter of the beads can be controlled, and the polymerization behavior can be stabilized.

In the method for producing methacrylic resin, it is preferable that the suspending agent is heated to 50 to 90 ℃ in advance and adjusted, and then the suspending agent is put into water (50 to 90 ℃) in the reactor. This makes it possible to adjust the average particle diameter and the variation of the methacrylic resin (e.g., methacrylic resin beads).

According to the method for producing methacrylic resin, an inorganic suspending agent is preferably used as compared with an organic suspending agent. In the case of an organic suspending agent, the variation in average particle diameter of the beads tends to be too small. Examples of the organic suspending agent include polyvinyl alcohol, methyl cellulose, ethyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, gelatin, and polyvinyl acetate.

The inorganic suspending agent preferably contains an inorganic compound containing calcium and/or aluminum in consideration of stability after dissolution in alkyl cyanoacrylate, for example, an inorganic compound such as calcium phosphate such as tricalcium phosphate (calcium phosphate), calcium carbonate, and aluminum hydroxide. In particular, from the viewpoint of stability after dissolution, an inorganic compound containing aluminum is more preferably contained.

In addition, the suspending agent can also contain suspending aids such as polyethylene glycol, sodium ethylenediamine tetraacetate, sodium lauryl sulfate and the like. The suspending agent may be contained in an amount of 0.01 to 10% by mass relative to 100% by mass of the suspending agent.

Preferably, the suspending agent is used in water in admixture with the monomer feed.

< washing method >)

In the method for producing methacrylic resin, it is preferable to perform an acid washing, water washing, alkali washing or the like to remove the suspending agent. The number of times of performing these washing operations may be selected to be the optimum number of times according to the work efficiency and the removal efficiency of the suspending agent, and may be repeated once or plural times.

The temperature at the time of washing may be selected to be an optimum temperature in consideration of the removal efficiency of the suspending agent, the degree of coloration of the resulting polymer, and the like, and is preferably 20 to 100 ℃. More preferably 30 to 95 ℃, still more preferably 40 to 95 ℃, particularly preferably 50 to 80 ℃.

In addition, from the viewpoints of washing efficiency, reduction of odor when used as a thickener, and dissolution stability in cyanoacrylate, the washing time per washing is preferably 10 to 180 minutes, more preferably 20 to 150 minutes.

The pH of the washing liquid used in washing is preferably from 1 to 12 as long as the pH is in a range where the suspending agent can be removed. The pH at the time of acid washing is preferably pH1 to 5, more preferably pH1.2 to 4, from the viewpoints of the removal efficiency of the suspending agent and the color tone of the polymer obtained. The acid used in this case is not particularly limited as long as it can remove the suspending agent, and conventionally known inorganic acids and organic acids can be used. Examples of the acid to be preferably used include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, boric acid, and the like, and the inorganic acid may be used as a diluted solution diluted with water or the like. Examples of the organic acid include organic acids having a carboxyl group, a sulfo group, a hydroxyl group, a mercapto group, and an enol. In view of the removal effect of the suspending agent and the color tone of the resulting resin, nitric acid, sulfuric acid, and an organic acid having a carboxyl group are more preferable.

After the acid washing, further water washing or alkali washing is preferably performed from the viewpoint of suppressing dissolution residue when dissolving in cyanoacrylate. More preferably, the washing is performed with warm water at 50℃or higher, and still more preferably, the washing is performed with warm water at 50℃or higher, and then the washing is performed with alkali and/or warm water at 50℃or higher.

By adjusting the pH of the slurry after washing to 2 or more and 9 or less, preferably 4 or more and 7 or less, more preferably 5 or more and 6.8 or less, and particularly preferably 5.5 or more and 6.5 or less, a thickener excellent in storage stability and light resistance even when dissolved in cyanoacrylate can be obtained.

(additive)

The tackifier of the present embodiment may optionally contain other additives. The additive is not particularly limited as long as it can exert the effect of the present invention, and may be appropriately selected according to the purpose.

Examples of the additive include, but are not limited to, ultraviolet absorbers, heat stabilizers, and light stabilizers; a plasticizer; a flame retardant; a flame retardant aid; a curing agent; a curing accelerator; an antistatic agent; a conductivity imparting agent; a stress relieving agent; a release agent; a crystallization accelerator; a hydrolysis inhibitor; a lubricant; an impact imparting agent; a slidability improver; a compatibilizer; a nucleating agent; a strengthening agent; a flow modifier; a dye; a sensitizer; a colorant; an anti-settling agent; anti-sagging agent; a filler; a defoaming agent; light diffusing particles; an antirust agent; an antimicrobial agent; a mildew inhibitor; an antifouling agent; conductive polymers, and the like.

The tackifier according to the present embodiment may be used as it is as the tackifier, or may be mixed with another methacrylic resin composition to be used as the tackifier.

The tackifier of this embodiment is particularly suitable for use as a cyanoacrylate (preferably alkyl cyanoacrylate, more preferably ethyl cyanoacrylate) tackifier.

The mass ratio of the methacrylic resin in the thickener is preferably 80 to 100 mass%, more preferably 90 to 100 mass%, and particularly preferably 99 to 100 mass% with respect to 100 mass% of the thickener.

< YI value of acetone solution >

The tackifier is obtained by dissolving the tackifier in acetone at a concentration of 10 mass%, and has a Yellowness Index (YI) value of preferably 0.1 to 2, more preferably 0.2 to 1.9, and still more preferably 0.3 to 1.8, as measured in a 1cm thick cell.

The YI value of the tackifier resin contained in the tackifier resin dissolved in acetone at a concentration of 10 mass% is preferably 0.1 to 2, more preferably 0.2 to 1.9, and even more preferably 0.3 to 1.8, as measured in a cell having a thickness of 1 cm.

By setting the YI value in the above range, an adhesive excellent in stability, hue, and light resistance after dissolution can be obtained. The YI value is set to the above range, and examples thereof include a method of obtaining a methacrylic resin by one-stage polymerization rather than two-stage polymerization.

< pH of aqueous phase when tackifier is dispersed in Water >

For the thickener, the pH of the supernatant aqueous phase measured under normal temperature conditions after stirring and dispersing 20g of the thickener and 100g of pure water and then allowing the mixture to stand to settle the solid content is preferably 2 to 9. The color phase when the thickener is dissolved and used is kept particularly good, the solubility in cyanoacrylate is improved, and the odor derived from the residue is suppressed, and is more preferably 3 or more, and particularly preferably 3.5 or more. From the viewpoint of improving storage stability after dissolution in cyanoacrylate or the like, it is preferably 8.5 or less, more preferably 8 or less, and particularly preferably 7.5 or less.

Further, it is preferable that the pH of the supernatant aqueous phase measured under normal temperature conditions after the solid content is settled by stirring and dispersing 20g of the methacrylic resin and 100g of pure water contained in the thickener and then standing is preferably 2 to 9. The color phase when the thickener is dissolved and used is kept particularly good, the solubility in cyanoacrylate is improved, and the odor derived from the residue is suppressed, and is more preferably 3 or more, and particularly preferably 3.5 or more. From the viewpoint of improving storage stability after dissolution in cyanoacrylate or the like, it is preferably 8.5 or less, more preferably 8 or less, and particularly preferably 7.5 or less.

< mass ratio of particles having a particle diameter of 710 μm or more >

From the viewpoint of obtaining a high solubility in cyanoacrylate-based adhesives, the mass ratio of particles having a particle diameter of 710 μm or more is preferably 5 mass% or less, more preferably 3 mass% or less, further preferably 1 mass% or less, particularly preferably 0.5 mass% or less, and particularly preferably 0.1 mass% or less, relative to 100 mass% of the thickener. The mass ratio of particles having a particle diameter of 710 μm or more can be measured by the method described in examples described later.

[ Adhesives ]

The tackifier of the present embodiment is preferably used for cyanoacrylate-based adhesives. Here, the cyanoacrylate-based adhesive includes the tackifier of the present embodiment and a cyanoacrylate (preferably an alkyl cyanoacrylate). Additives may also be present.

The viscosity of the adhesive at 25℃is preferably 0.5 to 10 Pa.s. Here, the viscosity is a viscosity measured by a B-type viscometer.

More preferably 1 to 9 Pa.s, and still more preferably 2 to 8 Pa.s. By reaching this range, an adhesive excellent in handleability can be obtained. Examples of the method for adjusting the viscosity of the adhesive to the above range include adjusting the weight average molecular weight of the methacrylic resin, adjusting the concentration of the methacrylic resin or the tackifier in the adhesive, and the like.

Specifically, the concentration is preferably 10 to 30% by mass, more preferably 12 to 28% by mass, and even more preferably 15 to 25% by mass, based on 100% by mass of the adhesive, of the solvent in cyanoacrylate (preferably alkyl cyanoacrylate, more preferably ethyl cyanoacrylate).

The temperature at the time of dissolution is preferably 30℃or higher from the viewpoint of easy dissolution, and preferably 80℃or lower from the viewpoint of stability.

Examples

The following examples and comparative examples will be described in more detail.

< raw materials >

The raw materials used are as follows.

Methyl Methacrylate (MMA): asahi chemical Co., ltd (2.5 mass ppm of 2, 4-dimethyl-6-t-butylphenol manufactured by China trade company as a polymerization inhibitor).

Methyl Acrylate (MA): mitsubishi chemical corporation (containing 15ppm of 4-methoxyphenol as a polymerization inhibitor).

Butyl Acrylate (BA): manufactured by east Asia Synthesis Co., ltd., which contains 15 mass ppm of 4-methoxyphenol as a polymerization inhibitor.

Styrene (St): manufactured by Asahi Kabushiki Kaisha (containing 12ppm of 4-t-butylcatechol as a polymerization inhibitor).

Ethylhexyl acrylate (EHA): manufactured by tokyo chemical industry company.

N-octyl mercaptan (NOM): manufactured by acarma corporation (archema).

Thioglycollic acid-2-ethylhexyl Ester (EHTG): manufactured by acarma corporation (archema).

Lauroyl Peroxide (LPO): manufactured by japan oil and fat company.

Tricalcium phosphate: manufactured by japan chemical industry corporation.

Calcium carbonate: nitto powder Industrial Co., ltd., NN #200, average particle diameter of 14.8 μm.

Sodium lauryl sulfate: fuji film and light purity chemicals were used as a suspension aid.

Tetra sodium ethylenediamine tetraacetate dihydrate (EDTA): manufactured by shima chemical company.

Aluminum hydroxide: the average particle diameters were adjusted by appropriately mixing SBX73, B303, B153, and B103 manufactured by japan light metals corporation.

[ production of methacrylic resin beads for use in tackifier ]

Example 1

Suspension adjustment

A vessel equipped with a stirrer equipped with 4 inclined blades was charged with 5kg of water, 130g of aluminum hydroxide having an average particle diameter of 33 μm, 0.39g of sodium lauryl sulfate and 2.3g of EDTA2, and mixed to obtain a mixed solution (a 1). The average particle diameter of the suspending agent in the mixed solution (a 1) was 33. Mu.m, and the pH of the obtained mixed solution (a 1) was 5.5. The resulting mixture (a 1) was heated to 70 ℃.

Polymerization reaction-

Subsequently, 25kg of water was charged into a 60L reactor and the temperature was raised to 80℃and a monomer solution obtained by mixing 3kg of the mixed solution (a 1), 21kg of the monomer raw material blended as shown in Table 1, 60g of EHTG, and 43g of LPO was charged into the reactor. Then, suspension polymerization was carried out while maintaining a temperature of about 80℃and an exothermic peak was observed after 140 minutes of charging the monomer solution. Then, after heating to 93℃at a rate of 1℃per minute, the temperature was maintained at about 93℃for 45 minutes, and the polymerization was substantially ended to obtain a polymer slurry. The resulting polymer slurry was then cooled to 50 ℃. To this polymer slurry, 20 mass% sulfuric acid was added to dissolve the suspending agent to obtain a polymerization reaction solution. Then, the resulting polymerization reaction solution was passed through a 1.68mm mesh sieve, aggregates were removed, and the resultant solution was filtered to separate into beaded methacrylic resin particles and a suspension waste liquid. The pH of the suspension waste was 3.3.

Washing process-

Then, addThe slurry polymer solution was obtained by adding ion-exchanged water at about 70℃in an amount approximately equal to that of the bead-like methacrylic resin particles, stirring, washing and filtering, and similarly, washing again with ion-exchanged water at about 70℃ (total of 2 times of water washing). An aqueous sodium hydroxide solution was added dropwise to the resulting slurry polymer solution, the pH was adjusted to 8.5, and the mixture was stirred and washed. The slurry polymer solution was filtered, and then ion-exchanged water at 70℃was added thereto, followed by stirring and washing. The pH of the resulting slurry polymer solution was 6.1. Then, the slurry polymer solution was filtered to obtain resin beads. The obtained resin beads were dried with a gas flow at 150℃in a gas flow (30 Nm ³ After drying in a fluidized bed dryer (25 Nm) ³ /hr) was dried at 90℃for 5 minutes to obtain methacrylic resin beads. The weight average molecular weight of the obtained methacrylic resin beads was 142000, mw/mn=1.9.

Example 2

The mixed solution (a 1) was prepared by the same method as in example 1. Next, a polymer slurry was formed and filtered in the same manner as in example 1 except that the blending of the monomer raw materials was changed as shown in table 1, to obtain bead-shaped methacrylic resin particles. Then, the washing was performed in the same manner as in example 1 except that the washing with water was performed 3 times, to obtain a slurry-like polymer solution. The pH of the resulting slurry polymer solution was 6.0. Then, the slurry polymer solution was filtered to obtain resin beads. The obtained resin beads were dried in the same manner as in example 1 to obtain methacrylic resin beads. The weight average molecular weight of the beads obtained was 136000, mw/mn=2.0.

Example 3, example 5

Methacrylic resin beads were obtained in the same manner as in example 1, except that the blending of the monomer raw materials was changed to the blending described in table 1.

Example 4

Methacrylic resin beads were obtained in the same manner as in example 1 except that the temperature of the pneumatic dryer was set to 100 ℃.

Comparative example 1

Methacrylic resin beads were obtained in the same manner as in example 1, except that the blending of the monomer raw materials was changed to MMA only.

Comparative example 2 polymerization example of two-stage polymerization

Into a vessel equipped with a stirrer equipped with 4 inclined blades, 2kg of water, 65g of tricalcium phosphate, 39g of calcium carbonate and 0.39g of sodium lauryl sulfate were charged to obtain a suspension (A). Monomer feed (1) was prepared by compounding 3900g of methyl methacrylate, 20g of butyl acrylate, 42g of EHTG, and 28g of LPO. Then, 26kg of water was charged into a 60L reactor and the temperature was raised to 80℃to charge the whole of the suspension (A) and the monomer raw material (1). Suspension polymerization was carried out at a temperature of about 80℃for 150 minutes, and the reaction was substantially ended to obtain a slurry of the polymer. Then, the slurry of the polymer (I) was stirred at 80℃for 60 minutes. Next, 20kg of methyl methacrylate, 100g of butyl acrylate, 35g of NOM and 40g of LPO were blended to prepare a monomer raw material (2). The monomer raw material (2) was charged into the reactor, followed by suspension polymerization at about 80℃for 90 minutes. Then, the temperature was raised to 92℃at a rate of 1℃per minute, and the reaction was maintained for 60 minutes, whereby the polymerization reaction was substantially ended to obtain a polymer slurry.

Then, filtration, washing and drying were carried out in the same manner as in example 1 to obtain methacrylic resin beads. The weight average molecular weight of the resulting methacrylic resin beads was 124000, mw/mn=2.6.

Example 6

Methacrylic resin beads were obtained by the same procedure as in example 1 except that the temperature of the ion-exchanged water was changed to about 25℃and the number of times of washing was 1. The pH of the washed slurry was 4.6.

Example 7

Methacrylic resin beads were obtained by the same procedure as in example 6 except that the amount of ion-exchanged water was changed to about half of that of the bead polymer and the number of washing times was 1. The pH of the slurry was 3.5.

Example 8

Methacrylic resin beads were obtained by the same procedure as in example 6 except that the washing was performed with a small amount of 20% by mass sulfuric acid, except for the ion-exchanged water. The pH of the slurry was 2.0.

Comparative example 3

The methacrylic resin particles and the suspension waste liquid were separated into beads by the same compounding and treatment as in example 3. Then, after adding water at normal temperature in an amount approximately equal to that of the bead-shaped methacrylic resin particles, an aqueous solution of sodium hydroxide was added to adjust the pH to 10.5, and the mixture was stirred, washed and filtered to obtain resin beads. The obtained resin beads were dried in the same manner as in example 3 to obtain methacrylic resin beads.

Example 9

The methacrylic resin particles and the suspension waste liquid were separated into beads by the same compounding and treatment as in example 1. Then, the same treatment as in comparative example 3 was carried out except that the pH was set to 9, to obtain methacrylic resin beads.

Comparative example 4

Methacrylic resin beads were obtained by the same compounding and polymerization method as in example 1, except that the temperature of the pneumatic dryer was set to 80 ℃.

Example 10

Suspending agent-

A vessel equipped with a stirrer equipped with 4 inclined blades was charged with 5kg of water, 130g of aluminum hydroxide having an average particle diameter of 23 μm, 0.39g of sodium lauryl sulfate and 2.3g of EDTA2, and mixed to obtain a mixed solution (a 2). The suspending agent in the mixed solution (a 2) had an average particle diameter of 23. Mu.m, and the pH of the obtained mixed solution was 5.5. The resulting mixture (a 2) was heated to 70 ℃. 27kg of water, 3kg of the mixed solution (a 2), 16kg of the monomer raw material, 13g of EHTG, and 25g of LPO in the mixing ratio shown in Table 2 were charged into a 60L reactor, and the mixture was mixed, and the reaction temperature in the reactor was set at 80℃for 150 minutes to polymerize, and then the mixture was heated to 93℃at a rate of 1℃per minute, and then cured for 45 minutes to substantially terminate the polymerization reaction, thereby obtaining a polymer syrup. Then, cooled to 50 ℃, 20 mass% sulfuric acid was charged to dissolve the suspending agent. Then, the polymerization reaction solution was passed through a 1.68mm mesh sieve to remove aggregates, and the resulting suspension was filtered through a filter cloth to separate into beaded methacrylic resin particles and a suspension waste liquid. Then, ion-exchanged water heated to 70℃in an amount approximately equal to that of the bead polymer was added thereto, and the operation was performed in the same manner as in example 1 to obtain resin beads. The weight average molecular weight of the obtained resin beads was 402000, and mw/mn=2.2.

Example 11

Methacrylic resin beads were obtained by the same composition and polymerization method as in example 10, except that the amount of EHTG in the monomer raw material was 8 g. The time from the monomer charge until the exothermic peak was observed was 120 minutes. The weight average molecular weight of the obtained resin beads was 654000, mw/mn=2.2.

Example 12

Methacrylic resin beads were obtained by the same composition and polymerization method as in example 10, except that the amount of water used was 30kg and polymerization was performed without adding EHTG. The time from the monomer charge until the exothermic peak was observed was 100 minutes. The weight average molecular weight of the obtained resin beads was 1250000, and mw/mn=2.4.

Examples 13, 14, 15 and 16

Methacrylic resin beads were obtained in the same manner as in example 1, except that the monomer raw materials were changed to the types and formulations shown in Table 3.

Comparative example 5

Into a vessel equipped with a stirrer equipped with 4 inclined blades, 2kg of water, 65g of tricalcium phosphate, 39g of calcium carbonate and 0.39g of sodium lauryl sulfate were charged to obtain a suspension (A). Then, 21kg of water was charged into a 60L reactor, the temperature was raised to 80℃and a suspension (A) and a mixed solution obtained by mixing 21kg of a monomer raw material, 60g of EHTG and 63g of LPO in the mixing ratio shown in Table 1 were charged. Then, suspension polymerization was carried out at about 80℃for 110 minutes, and then, after heating to 93℃at a rate of 1℃per minute, the polymerization reaction was substantially ended at a temperature of about 93℃for 45 minutes, thereby obtaining a polymer slurry. The polymerization time is shortened due to the increased amount of initiator LPO. Then, the mixture was cooled to 50℃and 20% by mass of sulfuric acid was charged to dissolve the suspending agent. Then, the polymerization reaction solution was filtered through a filter cloth and separated into beads Methacrylic resin particles and a suspension waste liquid. The pH of the suspension waste liquid at this time was 3.3. Then, ion-exchanged water heated to about 70℃was added in an amount approximately equal to that of the bead polymer, and stirring, washing and filtration were performed, and similarly, washing operation was performed again with ion-exchanged water at about 70℃to obtain a slurry-like polymer solution (total of 2 times of water washing). An aqueous sodium hydroxide solution was added dropwise to the resulting slurry polymer solution, and the pH was adjusted to 8.5, followed by stirring and washing. Filtering with a filter cloth, adding ion exchange water heated to 70 ℃, stirring and washing, and obtaining a slurry polymer solution with pH of 6.1. Then, the mixture was filtered through a filter cloth to obtain resin beads. The obtained undried resin beads were dried with a gas flow at 150℃using a gas flow dryer (30 Nm ³ After drying in a fluidized bed dryer (25 Nm) ³ /hr) drying at 90deg.C for 5 min to obtain methacrylic resin beads. The proportion of particles of 710 μm or more in the beads obtained was 5.1%.

Example 17

Suspension adjustment

Polymerization reaction-

Subsequently, 25kg of water was charged into a 60L reactor and the temperature was raised to 80℃and a monomer solution obtained by mixing 3kg of the mixed solution (a 1), 21kg of the monomer raw material blended as shown in Table 1, 60g of EHTG, and 43g of LPO was charged into the reactor. Then, suspension polymerization was carried out while maintaining a temperature of about 80℃and an exothermic peak was observed after 140 minutes of charging the monomer solution. Then, after heating to 93℃at a rate of 1℃per minute, the temperature was maintained at about 93℃for 45 minutes, and the polymerization was substantially ended to obtain a polymer slurry. The resulting polymer slurry was then cooled to 50 ℃. To this polymer slurry, 20 mass% sulfuric acid was added to dissolve the suspending agent to obtain a polymerization reaction solution. Next, the obtained polymerization reaction solution was passed through a 1.68mm mesh sieve, and the aggregates were removed, filtered, and separated into bead-like methacrylic resin particles and a suspension waste liquid. The pH of the suspension waste was 3.3.

Washing process-

Then, approximately the same amount of ion-exchanged water at about 70℃as that of the bead-shaped methacrylic resin particles was added, and stirring, washing and filtration were performed, and similarly, washing was performed again with ion-exchanged water at about 70℃ (total of 2 times of water washing) to obtain a slurry-like polymer solution. An aqueous sodium hydroxide solution was added dropwise to the resulting slurry polymer solution, the pH was adjusted to 8.5, and the mixture was stirred and washed. The slurry polymer solution was filtered, and then ion-exchanged water at 70℃was added thereto, followed by stirring and washing. The pH of the resulting slurry polymer solution was 6.1. Then, the slurry polymer solution was filtered to obtain resin beads. The obtained resin beads were dried with a gas flow at 150℃in a gas flow (30 Nm ³ After drying in a fluidized bed dryer (25 Nm) ³ /hr) was dried at 90℃for 5 minutes to obtain methacrylic resin beads. The weight average molecular weight of the obtained methacrylic resin beads was 143000, mw/mn=1.9. As a result of the NMR measurement, it was confirmed that a methacrylic resin having a composition shown by the charge was obtained.

Examples 18 to 24

Methacrylic resin beads were obtained in the same manner as in example 17, except that the blending of the monomer raw materials was changed to the blending described in table 1.

Example 25

Suspending agent-

A vessel equipped with a stirrer equipped with 4 inclined blades was charged with 5kg of water, 130g of aluminum hydroxide having an average particle diameter of 23 μm, 0.39g of sodium lauryl sulfate and 2.3g of EDTA2, and mixed to obtain a mixed solution (a 2). The suspending agent in the mixed solution (a 2) had an average particle diameter of 23. Mu.m, and the pH of the obtained mixed solution was 5.5. The resulting mixture (a 2) was heated to 70 ℃. 27kg of water, 3kg of the mixed solution (a 2), 16kg of the monomer raw material, 13g of EHTG, and 25g of LPO in the mixing ratio shown in Table 1 were charged into a 60L reactor, and the mixture was mixed, and the reaction temperature in the reactor was set at 80℃for 150 minutes to polymerize, and then the mixture was heated to 93℃at a rate of 1℃per minute, and then cured for 45 minutes to substantially terminate the polymerization reaction, thereby obtaining a polymer syrup. Then, the mixture was cooled to 50℃and 20% by mass of sulfuric acid was charged to dissolve the suspending agent. Then, the polymerization reaction solution was passed through a 1.68mm mesh sieve to remove aggregates, and the resulting suspension was filtered through a filter cloth to separate into beaded methacrylic resin particles and a suspension waste liquid. Then, ion-exchanged water was added in an amount approximately equal to that of the bead polymer and the temperature was raised to 70℃and the procedure was then carried out in the same manner as in example 17 to obtain methacrylic resin beads. The weight average molecular weight of the obtained methacrylic resin beads was 403000, mw/mn=2.3.

Example 26

Methacrylic resin beads were obtained by the same composition and polymerization method as in example 9, except that the amount of EHTG was 8 g. The time from the monomer charge until the exothermic peak was observed was 120 minutes. The weight average molecular weight of the obtained methacrylic resin beads was 653000, and mw/mn=2.2.

Example 27

Methacrylic resin beads were obtained by the same composition and polymerization method as in example 9, except that the amount of water used was 30kg and polymerization was performed without adding EHTG. The time from the monomer charge until the exothermic peak was observed was 100 minutes. The weight average molecular weight of the obtained methacrylic resin beads was 1250000, mw/mn=2.4.

Comparative example 6, 7

Methacrylic resin beads were obtained in the same manner as in example 17, except that the blending of the monomer raw materials was changed to the blending described in table 4.

[ physical Properties of methacrylic resin ]

(II-1) (weight average molecular weight, molecular weight distribution)

The weight average molecular weight and molecular weight distribution of the methacrylic resin beads obtained in examples and comparative examples were measured under the following apparatus and conditions.

Measurement device: gel permeation chromatography (HLC-8320 GPC) manufactured by Tosoh Co., ltd.) column: TSKguardcolumn SuperH-H1, TSKgel SuperHM-M2 and TSKgel SuperH2500 were used in series in this order.

In this column, the high molecular weight elutes fast and the low molecular weight elutes for a slow period of time.

A detector: RI (differential refractive) detector.

Detection sensitivity: 3.0mV/min.

Chromatographic column temperature: 40 ℃.

Sample: 0.02g of methacrylic resin in 20mL of tetrahydrofuran.

Injection amount: 10 mu L.

Developing solvent: tetrahydrofuran, flow rate; 0.6mL/min.

As an internal standard, 0.1g/L of 2, 6-di-tert-butyl-4-methylphenol (BHT) was added.

As standard samples for the standard curve, the following ten polymethyl methacrylates (manufactured by Polymer laboratories (Polymer Laboratories); PMMA calibration kit (PMMACalibration Kit) M-M-10) were used, the peak molecular weights of which were monodisperse and which were different.

	Peak molecular weight (Mp)
		Standard reagent 1	1916000
Standard reagent 2	625500
		Standard reagent 3	298900
Standard reagent 4	138600
		Standard reagent 5	60150
Standard reagent 6	27600
		Standard reagent 7	10290
Standard reagent 8	5000
		Standard reagent 9	2810
Standard reagent 10	850

Under the above conditions, the RI detection intensity relative to the elution time of the methacrylic resin was measured.

The weight average molecular weight (Mw) and the molecular weight distribution (Mw/Mn) of the methacrylic resin were obtained based on the area of the region in the GPC elution curve and the standard curve of the three-dimensional approximation expression.

(II-2) (volume average particle diameter, D ₁₀ )

Measured under the same conditions as in paragraph [0045] of Japanese patent application laid-open No. 2021-017561.

(II-3) (moisture Rate)

10.0g of methacrylic resin beads were kept at 70℃using a Shimadzu moisture meter (SHIMADZU MOISTURE BALANCE MOC-120H), and after the weight reduction rate of 10 seconds was 0.02% or less, the measurement was completed, and the total weight reduction rate was taken as the moisture rate.

(II-4) (MMA volatilization amount)

MMA volatiles were determined using GC-6890, MSD-5973 manufactured by Agilent corporation. Methacrylic resin beads 5mg were heated at 60℃for 10 minutes by a thermal decomposition furnace, and the resultant gas was captured by a liquid nitrogen-cooled column HP 5-MS. The captured gas fractions produced were analyzed by GC/MS and the amount of MMA volatilization was quantified.

(II-5) (YI value of acetone solution)

The obtained methacrylic resin beads were dissolved in acetone at a concentration of 10% by mass, and the YI value was measured in accordance with JIS K7105 using a color difference meter (TC-8600A, light source: 10-C, manufactured by Tokyo electric Co., ltd.) in a cell having a thickness of 1 cm.

(II-6) (pH of aqueous phase when tackifier is dispersed in water)

The pH of the supernatant was measured at room temperature after dispersing 20g of methacrylic resin beads and 100g of pure water and allowing the mixture to stand to settle the solid content.

Measurement device: PH meter F-52 (HORIBA ).

An electrode: standard ToupH electrodes 9615S-10D.

(II-7) (proportion of particles of 710 μm or more)

Using approximately 100g of methacrylic resin beads, the weight of particles remaining on each sieve when the sieve was sieved with a sieve test machine TSK B-1 by vibration force MAX for 10 minutes was measured using a sieve (JTS-200-45-31 (sieve mesh 710 μm), JTS-200-45-44 (sieve mesh 500 μm), 35 (sieve mesh 355 μm), 36 (sieve mesh 300 μm), 37 (sieve mesh 250 μm), 38 (sieve mesh 150 μm), 61 (tray)), and the proportion of particles remaining on the sieve of sieve mesh 710 μm (particle diameter component proportion of 710 μm or more) was measured. The measurement was performed three times, and the ratio was calculated from the average value.

[ proportion of particles of 710 μm or more ] =100× [ weight of particles remaining on a sieve having a mesh of 710 μm ]/[ weight of sample supplied to a screening tester ] (%)

(II-8) (viscosity of ethyl cyanoacrylate solution)

Silicone oil was placed in an oil bath with a stirrer and heated to 50 ℃. To a 110mL screw bottle (diameter: 50 mm) were added 16g of a tackifier, 64g of ethyl cyanoacrylate (in the case of 20 mass% of the tackifier), and a rotor, and the cap of the screw bottle was closed. A screw bottle was placed in an oil bath, and a stirrer was rotated (150 rpm), whereby methacrylic resin beads were dissolved in ethyl cyanoacrylate to obtain a slurry of an ethyl cyanoacrylate solution as a methacrylic resin. When the concentration of the thickener was 10 mass%, the thickener was dissolved at a rate of 8g of the thickener and 72g of ethyl cyanoacrylate. A tackifier having a weight average molecular weight of 85000 or more and less than 300000 is dissolved in ethyl cyanoacrylate at a concentration of 20 mass%, a tackifier having a weight average molecular weight of 300000 or more and less than 800000 is dissolved at a concentration of 10 mass%, a tackifier having a weight average molecular weight of 300000 or more and less than 800000 is dissolved at a concentration of 7 mass%, and the mixture is cooled and measured at 25 ℃ to obtain a viscosity η1. The slurry was left at 60℃for 48 hours, and then the viscosity η2 was measured at 25 ℃. The viscosity measurement apparatus used a type B viscometer (an carry forward precision mechanism, a digital viscometer LVDV Next). The slurry was measured and placed in a 40mL measuring tube, and the measuring tube was set on a viscometer to start the viscosity measurement. The viscosity was measured at 60rpm of the spindle. When the rotation speed is 60rpm out of the measurement range, the rotation speed is reduced to perform measurement. The amount of the slurry to be added may be adjusted to an appropriate viscosity when the slurry is produced.

[ III. Evaluation of tackifier ]

The following evaluation was performed using the methacrylic resin beads obtained in examples and comparative examples as a tackifier.

(III-1) (odor)

400g of methacrylic resin beads were placed in a polyethylene container (closed, 500mL jar (IBOY)), heated at 60℃for 2 hours, cooled to 30℃and then smelled by 5 panelists, and the number of points was evaluated according to the following criteria. The intensity of the scent was then ranked as a-D based on the average of the number of points of 5 persons.

6: an unacceptable odor.

5: very pungent odor.

4: a pungent odor.

3: feel intense, but not harsh.

2: feel (slightly) pungent.

1: it is difficult to feel.

The evaluation was performed by 5 persons, and the average value thereof was set as follows.

A (very weak odor): the average value of the points is 2 or less.

B (very weak odor): the average value of the points is more than 2 and less than 3.

C (good): the average value of the number of points is more than 3 and not more than 4.

D (bad): the average value of the points is more than 4.

(III-2) (dissolution rate)

Silicone oil was placed in an oil bath with a stirrer and heated to 50 ℃. To a 110mL screw bottle (diameter: 50 mm) were added 16g of a tackifier, 64g of ethyl cyanoacrylate (in the case of 20 mass% of the tackifier), and a rotor, and the cap of the screw bottle was closed. The screw flask was placed in an oil bath, the stirrer was rotated (150 rpm) and measurement was started. The time until the tackifier in the bottle was dissolved in ethyl cyanoacrylate was measured. The tackifiers having a weight average molecular weight of 85000 or more and less than 300000 were dissolved in ethyl cyanoacrylate at a concentration of 20 mass%, the tackifiers having a weight average molecular weight of 300000 or more and less than 800000 were dissolved at a concentration of 10 mass%, and the tackifiers having a weight average molecular weight of 300000 or more and less than 800000 were dissolved at a concentration of 7 mass%, and the order of the dissolution times was A to D.

A: the tackifier is completely dissolved within 45 minutes.

B: the tackifier is completely dissolved within 60 minutes.

C: over 60 minutes, the tackifier is substantially dissolved.

D: the tackifier was not dissolved.

(III-3) (long term stability after dissolution)

As in the above, the methacrylic resin beads were dissolved in ethyl cyanoacrylate at 50℃at respective concentrations corresponding to the molecular weights to prepare samples. After the sample was left at 25℃for 90 days, the long-term stability was evaluated as follows.

A (extremely excellent long-term stability): the sample remained fluid and could be used as an adhesive without problems.

B (excellent long-term stability): the fluidity of the sample was slightly lowered, but the sample was usable as an adhesive without problems.

C (good long-term stability): the flowability of the sample is reduced but uncured, enabling coating and adhesion.

D (poor long-term stability): the sample was cured.

(III-4) (light resistance)

For the evaluation of long-term stability, a sample dissolved in ethyl cyanoacrylate was partially extracted, placed in a sealed transparent 100mL container, and left outdoors for 1 month under direct sunlight. After the setting, the light resistance was evaluated according to the following criteria, based on the state of the sample. The light fastness of benchmarks A and B is acceptable.

A: the sample remained fluid.

B: the flowability of the sample is significantly reduced.

C: the sample was cured.

TABLE 1

TABLE 2

TABLE 3 Table 3

TABLE 4 Table 4

When example 1 was compared with comparative example 1 and example 8 with comparative examples 2 and 3, it was found that the stability after dissolution was excellent due to the low η ratio. When example 1 was compared with comparative example 4, it was found that the stability after dissolution was excellent due to the low ratio of η, and that the odor after dissolution of cyanoacrylate was reduced by the inclusion of a predetermined amount of the alkyl acrylate monomer having an alkyl group having 4 or more carbon atoms.

Industrial applicability

Claims

1. A tackifier comprising a methacrylic resin having a weight average molecular weight Mw of 85000 ～ 1500000, wherein,

the viscosity of the ethyl cyanoacrylate solution of the methacrylic resin at 25 ℃ is defined as eta 1, the viscosity unit is Pa.s,

the solution was allowed to stand at 60℃for 48 hours, cooled to 25℃and the viscosity of the cooled solution at 25℃was set to eta 2, the viscosity unit being Pa.s,

η1 and η2 satisfy: 1.0.ltoreq.eta.2/eta.1.ltoreq.5.0,

and, when the Mw of the methacrylic resin is 85000 or more and less than 300000, the concentration of the methacrylic resin of the solution is 20 mass%,

when the Mw of the methacrylic resin is 300000 or more and less than 800000, the concentration of the methacrylic resin of the solution is 10 mass%,

when the Mw of the methacrylic resin is 800000 or more and 1500000 or less, the concentration of the methacrylic resin of the solution is 7 mass%.

2. The adhesion promoter of claim 1,

the methacrylic resin contains 90 to 99.9 mass% of methyl methacrylate monomer units and 0.1 to 10 mass% of alkyl acrylate monomer units.

3. The adhesion promoter of claim 2, wherein,

the alkyl group of the alkyl acrylate monomer unit has a carbon number of 4 or more.

4. The adhesion promoter of claim 1, wherein,

the methacrylic resin contains 90 to 99.9 mass% of methyl methacrylate monomer units and 0.1 to 10 mass% of aromatic vinyl compound monomer units.

5. The adhesion promoter of claim 4, wherein,

The methacrylic resin contains 90 to 99.8 mass% of methyl methacrylate monomer units, 0.1 to 8 mass% of aromatic vinyl compound monomer units, and 0.1 to 8 mass% of acrylate monomer units.

6. The adhesion promoter of claim 5, wherein,

7. The adhesion promoter according to claim 1 or 2, wherein,

the moisture content of the methacrylic resin measured by a drying method is 0.01% or more and 1% or less.

8. The adhesion promoter of claim 1, wherein,

the methacrylic resin is in the form of beads having an average particle diameter of 50 to 500 μm.

9. The adhesion promoter of claim 8, wherein,

the mass ratio of particles having a particle diameter of 710 μm or more to 100 mass% of the thickener is 5 mass% or less.

10. A cyanoacrylate-based adhesive composition, wherein,

the cyanoacrylate-based adhesive composition comprises 1 to 30% of the tackifier according to claim 1.