Repair method for roadbed

Abstract

Provided is a repair method for a roadbed in a pavement body comprising a roadbed and a pavement layer provided on the roadbed, the repair method comprising a step for injecting a radical curing acrylic resin composition into the roadbed. Provided is a repair method further comprising, before the step, a step for obtaining the radical curing acrylic resin composition by mixing a main agent and a curing agent. With these repair methods, a roadbed can be repaired quickly even in a low-temperature environment, and the compressive strength of the roadbed after repair is excellent, and thus the repair methods can be suitably applied to repair methods for various types of roadbeds.

Description

Roadbed repair method

[0001] The present invention relates to a method for repairing a roadbed.

[0002] Pavements such as roads comprise a roadbed and a pavement layer laid on the roadbed. As the pavement is used for a long period of time, the roadbed may crack or weaken due to fatigue. One method for repairing such roadbed damage is to cut the pavement and replace it, including the roadbed and the pavement layer. However, this method has the drawback of requiring a long construction time and being expensive.

[0003] In response to this, for example, Patent Document 1 discloses a method in which a roadbed reinforcement material, mainly consisting of a hardening resin-based fluid or a mixed fluid obtained by mixing cement with a hardening resin-based fluid, is injected into the roadbed layer of the pavement at low pressure through an injection pipe, or is allowed to seep in from above, or is mixed with the roadbed material at the current location, thereby strengthening the bearing capacity of the roadbed layer.

[0004] Patent No. 3372280

[0005] Patent Document 1 states that it is preferable to use an epoxy resin-based reinforcing material when the roadbed layer needs to be particularly reinforced. However, according to the inventors' investigations, when an epoxy resin-based reinforcing material is used, the compressive strength of the roadbed after repair is not necessarily sufficient, and there are also problems in that the hardening time is long in a low-temperature (e.g., 5°C) environment.

[0006] Therefore, an object of one aspect of the present invention is to provide a roadbed repair method that can quickly repair a roadbed even in a low-temperature environment and that provides excellent compressive strength to the roadbed after repair.

[0007] The present inventors have found that by repairing a roadbed using a radically curable acrylic resin composition, the roadbed can be repaired quickly even in a low-temperature environment, and the compressive strength of the repaired roadbed is also excellent.

[0008] The present invention includes the following aspects. [1] A method for repairing a roadbed in a pavement comprising a roadbed and a pavement layer provided on the roadbed, the repair method comprising a step of injecting a radical-curable acrylic resin composition into the roadbed. [2] The repair method according to [1], wherein the radical-curable acrylic resin composition contains a resin having a (meth)acryloyl group. [3] The repair method according to [1] or [2], wherein the radical-curable acrylic resin composition further contains an ethylenically unsaturated monomer having a (meth)acryloyl group. [4] The repair method according to any one of [1] to [3], further comprising a step of mixing a base agent and a curing agent to obtain the radical-curable acrylic resin composition before the step of injecting the radical-curable acrylic resin composition.

[0009] According to one aspect of the present invention, it is possible to provide a roadbed repair method that can quickly repair a roadbed even in a low-temperature environment and that results in excellent compressive strength of the roadbed after repair.

[0010] One embodiment of the present invention is a method for repairing a roadbed in a pavement comprising a roadbed and a pavement layer provided on the roadbed, the repair method comprising a step of injecting a radical-curable acrylic resin composition into the roadbed from the pavement layer side (hereinafter also referred to as the "injection step").

[0011] In addition to the roadbed and pavement layer, the pavement may further comprise a road body and a subgrade. Such a pavement may comprise a road body, a subgrade, a roadbed, and a pavement layer in this order. The roadbed may have a lower subgrade located on the roadbed side and an upper subgrade located on the pavement layer side. The pavement layer may have a base layer located on the roadbed side and a surface layer located on the opposite side of the roadbed (the surface side of the pavement).

[0012] In one embodiment, in the injection step, a hole is drilled using core boring or the like, penetrating from the pavement layer (surface layer) side of the pavement body to the roadbed, an injection pipe is inserted, and the radical-curable acrylic resin composition can be injected through the injection pipe from the pavement layer side to the roadbed.

[0013] In another embodiment, in the injection step, an injection pipe can be inserted into the roadbed from the side of the pavement (e.g., a side road of a road), and the radical-curable acrylic resin composition can be injected into the roadbed from the side through the injection pipe.

[0014] In the injection step, the radical-curable acrylic resin composition may be injected into either the upper subgrade or the lower subgrade, and is preferably injected into the upper subgrade.

[0015] The radical-curable acrylic resin composition contains a (meth)acrylic resin that is cured (polymerized) by radicals. Such a (meth)acrylic resin may be a resin having a (meth)acryloyl group (hereinafter also referred to as "(meth)acrylate resin (A)").

[0016] Examples of the (meth)acrylate resin (A) include a urethane (meth)acrylate resin (A-1), an epoxy (meth)acrylate resin (A-2), a polyester (meth)acrylate resin (A-3), etc. These (meth)acrylate resins (A) may be used alone or in combination of two or more.

[0017] The urethane (meth)acrylate resin (A-1) is, for example, a reaction product of polyisocyanate (a), polyether polyol (b), and hydroxyalkyl (meth)acrylate (c), and has a (meth)acryloyl group at the end (the production method will be described in detail later).

[0018] Examples of the polyisocyanate (a) include 2,4-tolylene diisocyanate and its isomer or mixture of isomers (hereinafter abbreviated as tolylene diisocyanate or TDI), diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, dicyclohexylmethane diisocyanate, tolidine diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, Burnock D-750, CRISBON NX (a product of DIC Corporation), DESMODUR L (a product of Sumitomo Bayer Ltd.), and CORONATE L (a product of Nippon Polyurethane Co., Ltd.), with TDI being particularly preferred.

[0019] Examples of the polyether polyol (b) include polypropylene glycol (hereinafter abbreviated as PPG), polytetramethylene glycol (hereinafter abbreviated as PTMG), and polyoxyethylene diol. The polyether polyol (b) is preferably PPG or PTMG from the viewpoint of improving compatibility with the polyester (meth)acrylate resin (A-3) described below when the latter is used in combination, particularly tensile properties at low temperatures, viscosity at low temperatures, and the like. The number average molecular weight of the polyether polyol (b) is preferably 400 or more, more preferably 400 or more, and preferably 3,000 or less. The number average molecular weight of the polyether polyol (b) is a value determined in terms of polystyrene using gel permeation chromatography (GPC).

[0020] Examples of the hydroxyalkyl (meth)acrylate (c) include 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate.

[0021] The urethane (meth)acrylate resin (A-1) may be an allyl ether group-containing urethane (meth)acrylate resin in which an allyl ether group has been introduced into the resin in order to improve anaerobic (odor-reducing) properties during curing. From the viewpoint of easy and suitable synthesis of the resin, the allyl ether group is preferably an allyl ether group derived from a hydroxyl group-containing allyl ether compound.

[0022] Examples of hydroxyl group-containing allyl ether compounds include allyl ether compounds of polyhydric alcohols such as ethylene glycol monoallyl ether, diethylene glycol monoallyl ether, triethylene glycol monoallyl ether, polyethylene glycol monoallyl ether, propylene glycol monoallyl ether, dipropylene glycol monoallyl ether, tripropylene glycol monoallyl ether, polypropylene glycol monoallyl ether, 1,2-butylene glycol monoallyl ether, 1,3-butylene glycol monoallyl ether, hexylene glycol monoallyl ether, octylene glycol monoallyl ether, trimethylolpropane diallyl ether, glycerin diallyl ether, and pentaerythritol triallyl ether. The hydroxyl group-containing allyl ether compound is preferably an allyl ether compound having one hydroxyl group.

[0023] From the viewpoint of further improving the tensile properties at low temperatures, viscosity at low temperatures, etc., the number average molecular weight of the urethane (meth)acrylate resin (A-1) is preferably 800 or more, more preferably 1,000, and is preferably 50,000 or less, more preferably 20,000 or less. The number average molecular weight of the urethane (meth)acrylate resin (A-1) is a value determined by gel permeation chromatography (GPC) in terms of polystyrene.

[0024] Examples of methods for producing the urethane (meth)acrylate resin (A-1) include a method in which a polyisocyanate (a) is reacted with a polyether polyol (b) preferably at an NCO / OH ratio of 2 to 1.5 to produce a high-molecular-weight polyisocyanate, which is then reacted with 2 to 2.1 moles of a hydroxyalkyl (meth)acrylate (c) to produce a urethane (meth)acrylate resin (A-1) having a (meth)acryloyl group at its terminal.

[0025] Another example of the production method is a method in which a hydroxyalkyl (meth)acrylate (c) is reacted with a polyisocyanate (a) to obtain a (meth)acryloyl group-containing monoisocyanate, and then the obtained (meth)acryloyl group-containing monoisocyanate is reacted with a polyether polyol (b) in the presence of a polyisocyanate as the case may be, to obtain a urethane (meth)acrylate resin (A-1) having a (meth)acryloyl group at its terminal.

[0026] Examples of methods for producing allyl ether group-containing urethane (meth)acrylate resins include reacting a polyisocyanate (a) with a polyether polyol (b), preferably at an NCO / OH ratio of 2 to 1.5, to produce a compound containing terminal isocyanate groups, and then reacting this compound with a hydroxyl group-containing acrylic compound and a hydroxyl group-containing allyl ether compound so that the hydroxyl groups are approximately equivalent to the isocyanate groups. In this case, the molar ratio of the hydroxyl group-containing methacrylic compound to the hydroxyl group-containing allyl ether compound is preferably 90 / 10 to 20 / 80, more preferably 70 / 30 to 40 / 60.

[0027] Other methods for producing an allyl ether group-containing urethane (meth)acrylate resin include, for example, a method in which a hydroxyl group-containing methacrylic compound and a hydroxyl group-containing allyl ether compound are reacted with a polyisocyanate, and then the resulting isocyanate group-containing compound is reacted with a polyether polyol (b) to produce an allyl ether group-containing polyether urethane (meth)acrylate resin.

[0028] A polymerization inhibitor may be added during or after the production of the urethane (meth)acrylate resin (A-1). Examples of polymerization inhibitors that can be used include toluhydroquinone, hydroquinone, benzoquinone, toluhydroquinone, p-tert-butylcatechol, and 2,6-tert-butyl-4-methylphenol. The amount of polymerization inhibitor added is preferably 100 ppm or more and preferably 200 ppm or less, based on 100 parts by mass of the urethane (meth)acrylate resin (A-1).

[0029] The epoxy (meth)acrylate resin (A-2) may be one obtained by reacting a bisphenol-type epoxy compound or a mixture of a bisphenol-type epoxy compound and a novolac-type epoxy compound with an unsaturated monobasic acid by a conventionally known method.

[0030] Examples of the bisphenol-type epoxy compound that can be used include a glycidyl ether-type epoxy compound having two or more epoxy groups per molecule obtained by reacting epichlorohydrin with bisphenol A or bisphenol F, a dimethylglycidyl ether-type epoxy compound obtained by reacting methylepichlorohydrin with bisphenol A or bisphenol F, and an epoxy compound obtained by reacting an alkylene oxide adduct of bisphenol A with epichlorohydrin or methylepichlorohydrin. These epoxy compounds may be used alone or in combination of two or more.

[0031] The novolac-type epoxy compound may be, for example, an epoxy compound obtained by reacting phenol novolac or cresol novolac with epichlorohydrin or methyl epichlorohydrin. These epoxy compounds may be used alone or in combination of two or more.

[0032] Examples of the unsaturated monobasic acid that can be used include (meth)acrylic acid, cinnamic acid, crotonic acid, monomethyl maleate, monopropyl maleate, monobutene maleate, sorbic acid, mono(2-ethylhexyl) maleate, etc. These unsaturated monobasic acids may be used alone or in combination of two or more.

[0033] The polyester (meth)acrylate resin (A-3) is a saturated polyester resin synthesized from a glycol and a dibasic acid, which has one or more (meth)acryloyl groups at its terminals, preferably one (meth)acryloyl group at each of its terminals.

[0034] The glycol is preferably an aliphatic or alicyclic glycol having two hydroxyl groups. Examples of the glycol include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, tetraethylene glycol, 2-methyl-1,3-propanediol, 1,3-butanediol, neopentyl glycol, hydrogenated bisphenol A, 1,4-butanediol, 1,6-hexanediol, 1,2,3,4-tetrahydroxybutane, glycerin, trimethylolpropane, 1,3-propanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexane glycol, 1,3-cyclohexane glycol, 1,4-cyclohexane glycol, 1,4-cyclohexanedimethanol, paraxylene glycol, bicyclohexyl-4,4'-diol, 2,6-decalin glycol, and 2,7-decalin glycol. The glycols may be used alone or in combination of two or more. As the glycol, adducts of ethylene oxide, propylene oxide, etc. may also be used.

[0035] Examples of dibasic acids include aliphatic dibasic acids (d1), alicyclic dibasic acids (d2), and aromatic dibasic acids (d3). The aliphatic dibasic acid (d1) is preferably adipic acid. Examples of alicyclic dibasic acids (d2) include hexahydrophthalic acid, hexahydrophthalic anhydride, hexahydroterephthalic acid, and hexahydroisophthalic acid. Examples of aromatic dibasic acids (d3) include phthalic acid, phthalic anhydride, halogenated phthalic anhydride, isophthalic acid, and terephthalic acid.

[0036] The content of the aliphatic dibasic acid (d1) (preferably the content of adipic acid) is preferably 40 mol % or more, more preferably 50 mol % or more, and preferably 100 mol % or less, based on the total amount of the dibasic acid.

[0037] The number average molecular weight of the polyester (meth)acrylate resin (A-3) is preferably not less than 2000 and preferably not more than 4000. The number average molecular weight of the polyester (meth)acrylate resin (A-3) is a value determined by gel permeation chromatography (GPC) in terms of polystyrene.

[0038] The polyester (meth)acrylate resin (A-3) can be produced, for example, by reacting a terminal functional group (hydroxyl group and / or carboxyl group) of a saturated polyester with a compound containing a functional group reactive with the functional group and a (meth)acryloyl group. Examples of the compound to be reacted include unsaturated monobasic acids such as glycidyl (meth)acrylate and (meth)acrylic acid, and glycidyl esters thereof. The compound is preferably glycidyl (meth)acrylate.

[0039] The radical-curable acrylic resin composition may further contain other resins. Examples of such other resins include an unsaturated polyester resin (B). When the unsaturated polyester resin (B) is used in combination with the urethane methacrylate resin (A), the polyester methacrylate resin (A-2), and the ethylenically unsaturated monomer (C), it can function as a compatibilizer that improves the compatibility of these components.

[0040] The unsaturated polyester resin (B) is preferably a dicyclopentadiene-based unsaturated polyester resin, which is obtained by reacting an α,β-unsaturated carboxylic acid and / or a saturated carboxylic acid with a polyhydric alcohol and dicyclopentadiene, from the viewpoint of particularly suitably exhibiting the above-mentioned function as a compatibilizer.

[0041] Examples of α,β-unsaturated carboxylic acids include fumaric acid, maleic acid, maleic anhydride, itaconic acid, citraconic acid, mesaconic acid, chloromaleic acid, and dimethyl esters thereof. These may be used alone or in combination of two or more. From the viewpoint of further improving compatibility, the α,β-unsaturated carboxylic acid is preferably maleic anhydride.

[0042] Examples of saturated carboxylic acids include phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, HET acid, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, adipic acid, sebacic acid, azelaic acid, etc. These may be used alone or in combination of two or more.

[0043] As the polyhydric alcohol, one or more of the glycols used in the synthesis of the polyester(meth)acrylate resin (A-3) can be used. From the viewpoint of further improving compatibility, the polyhydric alcohol is preferably ethylene glycol or diethylene glycol.

[0044] Examples of methods for producing dicyclopentadiene-based unsaturated polyester resins include a method in which an α,β-unsaturated carboxylic acid and / or a saturated carboxylic acid, a polyhydric alcohol, and dicyclopentadiene are all charged into a reaction system and subjected to a condensation reaction, and a method in which an α,β-unsaturated carboxylic acid and / or a saturated carboxylic acid is first reacted with dicyclopentadiene, and then a polyhydric alcohol is supplied and subjected to a condensation reaction. The condensation reaction is preferably carried out in an inert gas atmosphere at a temperature of 150 to 250°C.

[0045] The reaction ratio of the α,β-unsaturated carboxylic acid and / or saturated carboxylic acid, the polyhydric alcohol, and the dicyclopentadiene is preferably in the range of 0.3 to 0.7 moles of the polyhydric alcohol and 0.7 to 1.3 moles of the dicyclopentadiene per mole of the α,β-unsaturated carboxylic acid and / or saturated carboxylic acid.

[0046] The acid value of the dicyclopentadiene-based unsaturated polyester resin obtained by the above method is preferably 10 mgKOH / g or more, preferably 40 mgKOH / g or less, more preferably 30 mgKOH / g or less. The acid value of the dicyclopentadiene-based unsaturated polyester resin is a value measured in accordance with JIS K1557-5.

[0047] The number average molecular weight of the unsaturated polyester resin (B) is preferably 1,000 or more, and preferably 40,000 or less, more preferably 10,000 or less, and even more preferably 3,000, from the viewpoint of further improving curability, viscosity, compatibility, etc.

[0048] The radical-curable acrylic resin composition may contain an ethylenically unsaturated monomer (C) having a (meth)acryloyl group. Examples of the ethylenically unsaturated monomer (C) having a (meth)acryloyl group include (meth)acrylic monomers having an alicyclic structure such as isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentenyloxyethyl (meth)acrylate; methyl (meth)acrylate, ethyl (meth)acrylate, propanol; propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, sec-butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylbutyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, n-octyl (meth)acrylate, nonyl (meth)acrylate, dodecyl (meth)acrylate, Aliphatic (meth)acrylic monomers such as 3-methylbutyl (meth)acrylate, isooctyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, neopentyl (meth)acrylate, hexadecyl (meth)acrylate, and isoamyl (meth)acrylate; (meth)acrylic monomers having an ether group such as 3-methoxybutyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 2-methoxybutyl (meth)acrylate, methoxypolyethylene glycol acrylate having an addition mole number of oxyethylene in the range of 1 to 15, ethoxy-diethylene glycol (meth)acrylate, and ethyl carbitol (meth)acrylate; (meth)acrylic monomers having a hydroxyl group such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate;Examples of (meth)acrylic monomers that can be used include aromatic (meth)acrylic monomers such as benzyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxy polyethylene glycol acrylate, phenyl (meth)acrylate, and 2-hydroxy-3-phenoxypropyl (meth)acrylate; and (meth)acrylic monomers having a nitrogen atom ((meth)acrylamide monomers) such as (meth)acrylamide, dimethyl (meth)acrylamide, acryloylmorpholine, dimethylaminopropyl (meth)acrylamide, isopropyl (meth)acrylamide, diethyl (meth)acrylamide, diacetone (meth)acrylamide, and hydroxyethyl acrylamide. Among these, acrylamide monomers are preferred because of their superior alkali resistance and photocurability. These (meth)acrylic monomers may be used alone or in combination of two or more.

[0049] The radical-curable acrylic resin composition preferably contains all of the above-mentioned (meth)acrylate resin (A), unsaturated polyester resin (B), and (meth)acryloyl group-containing ethylenically unsaturated monomer (C).

[0050] The mass ratio ((A) / (C)) of the content of the (meth)acrylate resin (A) to the content of the ethylenically unsaturated monomer (C) having a (meth)acryloyl group is preferably 10 / 90 or more, more preferably 30 / 70 or more, and is preferably 90 / 10 or less, more preferably 70 / 30 or less.

[0051] The mass ratio ((A+B) / (C)) of the total content of the methacrylate resin (A) and the unsaturated polyester resin (B) to the content of the ethylenically unsaturated monomer (C) having a (meth)acryloyl group is preferably 20 / 80 or more, more preferably 40 / 60 or more, and is preferably 8 / 2 or less, more preferably 70 / 30 or less, from the viewpoint of further improving curability and viscosity.

[0052] From the viewpoint of further improving compressive strength, the content of the unsaturated polyester resin (B) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more, relative to 100 parts by mass in total of the urethane (meth)acrylate resin (A-1), the epoxy (meth)acrylate resin (A-2), and the polyester (meth)acrylate resin (A-3), and is preferably 25 parts by mass or less, and more preferably 20 parts by mass or less.

[0053] The radical curable acrylic resin composition may further contain a radical curing agent. The radical curing agent is preferably an organic peroxide. Examples of the organic peroxide include diacyl peroxides, peroxyesters, hydroperoxides, dialkyl peroxides, ketone peroxides, peroxyketals, alkyl peresters, and percarbonates. The organic peroxide is a diacyl peroxide, preferably benzoyl peroxide.

[0054] The content of the radical curing agent is preferably 0.01 parts by mass or more and preferably 4 parts by mass or less relative to 100 parts by mass of the total amount of the curable components (when the radical curable acrylic resin composition contains the above-mentioned (meth)acrylate resin (A), unsaturated polyester resin (B), and ethylenically unsaturated monomer (C) having a (meth)acryloyl group, (A), (B), and (C); the same applies hereinafter).

[0055] The radical-curable acrylic resin composition preferably further contains a curing accelerator. The curing accelerator decomposes the radical curing agent (organic peroxide) through a redox reaction, facilitating the generation of active radicals. Examples of the curing accelerator include tertiary amines, quaternary ammonium salts, and mercaptans. The curing accelerator is preferably a tertiary amine.

[0056] Examples of tertiary amines include aniline, N,N-dimethylaniline, N,N-diethylaniline, p-toluidine, N,N-dimethyl-p-toluidine, N,N-bis(2-hydroxyethyl)-p-toluidine (abbreviated as PTD-2EO), N-methyl-N-(2-hydroxyethyl)-p-toluidine, N-ethyl-N-(2-hydroxyethyl)-p-toluidine, N-methyl-N-(2-hydroxyethyl)-m-toluidine, N-ethyl-N-(2-hydroxyethyl)-m-toluidine, 4-(N,N-dimethylamino)benzaldehyde, Examples of the tertiary amine include N,N-substituted anilines such as 4-[N,N-bis(2-hydroxyethyl)amino]benzaldehyde, 4-(N-methyl-N-hydroxyethylamino)benzaldehyde, N,N-bis(2-hydroxypropyl)-p-toluidine, N-ethyl-m-toluidine, triethanolamine, m-toluidine, diethylenetriamine, pyridine, phenylimorpholine, piperidine, N,N-bis(hydroxyethyl)aniline, and diethanolaniline, N,N-substituted-p-toluidine, and 4-(N,N-substituted amino)benzaldehyde. The tertiary amine is preferably N,N-substituted-p-toluidine, and more preferably PTD-2EO.

[0057] The content of the curing accelerator is preferably 0.1 parts by mass or more, and preferably 3 parts by mass or less, and more preferably 1 part by mass or less, per 100 parts by mass of the total of the curable components.

[0058] The radical-curable acrylic resin composition may further contain other additives, such as thermoplastic resins, paraffins and / or waxes, fillers, aggregates, colorants (pigments, dyes, etc.), fiber reinforcing materials, etc.

[0059] The viscosity of the radical-curable acrylic resin composition is preferably as low as possible, since this allows the composition to be more easily injected into the roadbed and further increases the compressive strength of the roadbed after repair. The viscosity of the radical-curable acrylic resin composition at 25°C is preferably 400 mPa·s or less, more preferably 300 mPa·s or less, even more preferably 200 mPa·s or less, and particularly preferably 100 mPa·s or less. The viscosity of the radical-curable acrylic resin composition at 25°C is measured using a Type I BM viscometer in Table 7 in accordance with JIS K6901:2008 "5.5.1 When using the Brookfield viscometer method."

[0060] The radical-curable acrylic resin composition is preferably obtained by mixing a base agent and a curing agent. In this case, the repair method according to one embodiment may further include a step of mixing the base agent and the curing agent to obtain the radical-curable acrylic resin composition (hereinafter also referred to as a "mixing step") before the injection step.

[0061] The main agent used in the mixing step contains at least a curable component. The curing agent used in the mixing step contains at least a radical curing agent. For example, when the radical-curable acrylic resin composition contains the above-mentioned urethane methacrylate (A-1), epoxy (meth)acrylate resin (A-2), polyester methacrylate (A-3), unsaturated polyester resin (B), ethylenically unsaturated monomer (C) having a (meth)acryloyl group, and a radical curing agent, the main agent contains the above-mentioned urethane methacrylate (A-1), epoxy (meth)acrylate resin (A-2), polyester methacrylate (A-3), unsaturated polyester resin (B), and ethylenically unsaturated monomer (C) having a (meth)acryloyl group, and the curing agent contains a radical curing agent.

[0062] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0063] (Preparation of radically curable acrylic resin composition (1)) A four-neck flask equipped with a stirrer, a reflux condenser, and a thermometer was charged with 10 parts by mass of epoxy methacrylate resin (A-1), 10 parts by mass of unsaturated polyester resin (B-1), 60 parts by mass of methyl methacrylate (MMA) (C-1), and 0.4 parts by mass of N,N-bis(2-hydroxyethyl)-p-toluidine (PTD-2EO), and the mixture was stirred at 80° C. until homogeneous. Thereafter, the mixture was filtered through a 200-mesh wire screen to obtain a radically curable acrylic resin composition (1).

[0064] The epoxy methacrylate resin (A-1) was synthesized by the following procedure: 1,850 parts by mass of Epiclon 850 (manufactured by DIC Corporation), which is an epoxy equivalent obtained by reacting bisphenol A with epichlorohydrin, 860 parts by mass of methacrylic acid, 1.36 parts by mass of hydroquinone, and 10.8 parts by mass of triethylamine were placed in a four-neck flask equipped with a thermometer, a stirrer, an inert gas inlet, and a reflux condenser, and the mixture was heated to 120°C and reacted for 10 hours to obtain an epoxy methacrylate resin (A-1) with an acid value of 3.5 mgKOH / g.

[0065] Furthermore, unsaturated polyester resin (B-1) was synthesized by the following procedure. 270 parts by mass of water, 2000 parts by mass of dicyclopentadiene, 0.5 parts by mass of hydroquinone, and 450 parts by mass of ethylene glycol were charged into a four-neck flask equipped with a thermometer, a stirrer, an inert gas inlet, and a reflux condenser, and the mixture was reacted at 80°C for 4 hours under a nitrogen stream. When the acid value reached 210 mgKOH / g, 1370 parts by mass of maleic anhydride was charged, and the mixture was reacted at 200°C for 6 hours, yielding unsaturated polyester resin (B-1) with an acid value of 8 mgKOH / g.

[0066] (Preparation of radically curable acrylic resin composition (2)) A radically curable acrylic resin composition (2) was obtained in the same manner as for the radically curable acrylic resin composition (1), except that the composition of the radically curable acrylic resin composition was changed as shown in Table 1.

[0067] The urethane methacrylate resin (A-2) was synthesized by the following procedure. 500 parts by mass of polypropylene glycol having a number average molecular weight of 1000 and 72 parts by mass of tolylene diisocyanate were charged into a reaction vessel equipped with a thermometer, a stirrer, an inert gas inlet, an air inlet, and a reflux condenser, and the mixture was reacted at 80°C for 2 hours under a nitrogen stream. When the NCO equivalent reached 600, almost the theoretical equivalent value, the mixture was cooled to 50°C. Under an air stream, 0.07 parts by mass of hydroquinone and 135 parts by mass of 2-hydroxyethyl methacrylate were added, and the mixture was reacted at 90°C for 4 hours. When the NCO% reached 0.1% or less, 0.07 parts by mass of tertiary butyl catechol was added, and urethane methacrylate resin (A-2) was obtained.

[0068] Furthermore, nBA (C-2) is n-butyl acrylate, and the paraffin wax is "Paraffin Wax-130" manufactured by Nippon Seiro Co., Ltd.

[0069] (Preparation of radically curable acrylic resin composition (3)) A radically curable acrylic resin composition (3) was obtained in the same manner as for the radically curable acrylic resin composition (1), except that the composition of the radically curable acrylic resin composition was changed as shown in Table 1.

[0070] The polyester methacrylate resin (A-3) was synthesized by the following procedure. A reaction vessel equipped with a thermometer, a stirrer, an inert gas inlet, and a reflux condenser was charged with 400 parts by mass of diethylene glycol, 200 parts by mass of phthalic anhydride, 660 parts by mass of 3-methyltetrahydrophthalic acid, 0.3 parts by mass of dibutyltin oxide, and 0.1 parts by mass of methylhydroquinone, and the mixture was reacted at 220°C for 4 hours. The mixture was cooled to 150°C, and 60 parts by mass of glycidyl methacrylate was added. The mixture was reacted at 130°C for 4 hours to obtain a polyester methacrylate resin (A-3) having a number average molecular weight of 5,000 and an acid value of 0.1 mgKOH / g.

[0071] 2-EHA is 2-ethylhexyl acrylate, and DICNATE-208V is "DICNATE-208V" (metal soap) manufactured by DIC Corporation.

[0072]

[0073] (Examples 1 to 3) In a 5°C environment, 100 parts by mass of each of the radical-curable acrylic resin compositions (1) to (3) prepared above (corresponding to the main component) was further mixed with 2 parts by mass of an organic peroxide ("Niper NS" manufactured by NOF Corporation) as a curing agent, and then each radical-curable acrylic resin composition was injected using a syringe into a Φ50 x 100 mm formwork (simulating the roadbed in a pavement) previously filled with No. 4 silica sand to obtain a test specimen.

[0074] Comparative Example 1 A test specimen was obtained by using a syringe to inject a cationically curable acrylic resin composition ("SFC-55" manufactured by DIC Corporation, emulsion, viscosity at 25°C: 100 mPa·s) into a Φ50×100 mm formwork that had been filled in advance with No. 4 silica sand in a 5°C environment.

[0075] Comparative Example 2 In a 5°C environment, an epoxy resin composition ("EXA-8728 / EXC-1281" manufactured by DIC Corporation, viscosity at 25°C: 300 mPa·s) was injected using a syringe into a Φ50×100 mm mold filled in advance with No. 4 silica sand to obtain a test specimen.

[0076] (Measurement of curing time and compressive strength) The surface of each obtained test specimen was checked by touch, and the time (minutes) required for curing and drying was recorded as the curing time. In addition, the compressive strength of each test specimen was measured 1 hour and 24 hours after preparation according to the method described in JIS A1108. The results are shown in Table 2.

[0077]

Claims

1. A method for repairing a roadbed in a pavement comprising a roadbed and a pavement layer provided on the roadbed, comprising: A repair method comprising a step of injecting a radically curable acrylic resin composition having a viscosity of 400 mPa·s or less at 25°C into the roadbed.

2. The repair method according to claim 1 , wherein the radically curable acrylic resin composition contains a resin having a (meth)acryloyl group.

3. The repair method according to claim 1 or 2, wherein the radical-curable acrylic resin composition contains an ethylenically unsaturated monomer having a (meth)acryloyl group.

4. The repair method according to claim 1 or 2, further comprising, before the step, a step of mixing a base agent and a curing agent to obtain the radical curable acrylic resin composition.