Building panel materials

Abstract

To form a cured product that does not suffer a significant decrease in elastic modulus even at high temperatures, from an acrylic resin composition that is low in viscosity compared to epoxy resin and the like and can also be cured at low temperatures.SOLUTION: An acrylic resin composition comprises a polymerizable compound comprising at least one monomer mi (1≤i≤N) and a curing agent and gives a cured product with the ratio of a storage modulus at 250°C to that at 25°C being 20% or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an acrylic resin composition and a building panel material.

Background Art

[0002] Fiber Reinforced Plastics (FRP) is a lightweight material with excellent formability and processability compared to ceramics and metal materials. However, on the other hand, its heat resistance is significantly inferior, and the temperature range in which FRP can be used as a structural material is quite low. Therefore, FRP using various high heat-resistant resins such as polyimide as a matrix has been mainly developed as aerospace materials as lightweight structural materials with heat resistance. However, high heat-resistant resins such as polyimide are inferior in formability and economy compared to general-purpose epoxy resins, etc., and there are few application examples outside the aerospace field. On the contrary, general-purpose epoxy resins are excellent in formability and economy, and have extremely good adhesion to carbon fibers, and have optimal properties as a matrix for FRP.

[0003] Non-Patent Document 1 reports that an epoxy resin (hereinafter also referred to as a Tg-less epoxy resin) in which the elastic modulus of the cured product hardly decreases even at high temperatures can be prepared by curing an epoxy resin with a potassium carboxylate salt. A cured product that maintains a glassy state even at high temperatures and does not change to a rubbery state can be said to have virtually no Tg.

[0004] Patent Document 1 proposes a polymerizable composition comprising an epoxy compound and a polymerization initiator, wherein the polymerization initiator consists of an alkali metal salt of a weak acid monomer having an organic group. Patent Document 2 proposes a polymerizable composition comprising a polyfunctional epoxy compound and a polymerization initiator, wherein the polymerization initiator consists of an alkali metal salt of a carboxylic acid, and a heat-resistant composite material comprising reinforcing fibers.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2006-63154 [Patent Document 2] International Publication No. 2006 / 046534 Pamphlet [Non-patent literature]

[0006] [Non-Patent Document 1] Journal of the Japan Society for Composite Materials, Vol. 33, No. 2 (2007), pp. 62-71, "High Heat-Resistant Composite Materials Using Tg-Free Epoxy Resin" [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, in the case of epoxy resins, it is necessary to use a polyfunctional, high-viscosity epoxy resin that is solid at room temperature, and curing is required at a high temperature of around 200°C. [Means for solving the problem]

[0008] In view of the above, one aspect of the present invention relates to an acrylic resin composition comprising a polymerizable compound and a curing agent, which produces a cured product in which the ratio of the storage modulus at 250°C to the storage modulus at 25°C is 20% or more.

[0009] Another aspect of the present invention relates to a building panel material comprising a Tg-less material comprising fibers and the acrylic resin composition impregnated in the fibers. [Effects of the Invention]

[0010] From an acrylic resin composition that has lower viscosity than epoxy resins and can be cured at low temperatures, it is possible to obtain a cured product (hereinafter also referred to as a Tg-less cured product) in which the elastic modulus does not decrease significantly even at high temperatures. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram of the structure of a building panel material relating to one embodiment of the present invention. [Modes for carrying out the invention]

[0012] The following embodiments of the acrylic resin composition will be described in detail, but these embodiments are not limiting to the present invention, and various changes and modifications are possible.

[0013] The acrylic resin composition according to this embodiment comprises a polymerizable compound containing one or more (N types) monomers mi (1 ≤ i ≤ N) and a curing agent. Here, i is an integer less than or equal to N. N is not particularly limited, but for example it can be 5 or less, 4 or less, or 3 or less. If the polymerizable compound contains, for example, two monomers, then i = 1 or 2, N = 2, and the polymerizable compound is a mixture of monomer m1 and monomer m2. Similarly, if the polymerizable compound contains three monomers, then i = 1, 2, or 3, N = 3, and the polymerizable compound is a mixture of monomer m1, monomer m2, and monomer m3. Here, a polymerizable compound refers to a compound having a functional group with a radically polymerizable carbon-carbon double bond. The polymerizable compound includes at least an acrylic polymerizable compound (hereinafter also referred to as an acrylic compound).

[0014] Acrylic compounds are a general term for compounds containing a (meth)acryloyloxy group or a (meth)acryloyl group. A (meth)acryloyl group means an acryloyl group, a methacryloyl group, or both. A (meth)acryloyloxy group means an acryloyloxy group, a methacryloyloxy group, or both. Similarly, "(meth)acrylic" means "acrylic" or "methacrylic" or both.

[0015] The acrylic compound may constitute substantially 99% to 100% by mass of the polymerizable compounds (total of one or more monomers mi (1 ≤ i ≤ N)) that make up the acrylic resin composition.

[0016] The acrylic resin composition according to this embodiment produces a cured product in which the ratio of the storage modulus at 250°C to the storage modulus at 25°C (hereinafter also referred to as the modulus retention rate R) is 20% or more. The higher the modulus retention rate R, the more desirable it is. The modulus retention rate R may be 20% or more, 30% or more, 40% or more, or 45% or more. On the other hand, the modulus retention rate R of the cured product of a general acrylic resin composition is 5% or less.

[0017] Note that the storage modulus at 25°C and the storage modulus at 250°C of the cured product can be measured using a commercially available measuring device and a sample of the cured product. For example, using a DMA measuring device (for example, DMS6100 manufactured by Hitachi High-Tech Science Corporation), by raising the temperature from -50°C to +350°C at a heating rate of 1 Hz and 2°C / min, the storage modulus at 25°C and 250°C of the cured product can be measured. The sample of the cured product may be prepared by molding the cured product obtained by sufficiently curing the acrylic resin composition into a shape suitable for the measuring device. The curing rate of the cured product of the acrylic resin composition used as the sample may be 90% or more (more preferably 95% or more). The curing rate is the ratio of the mass of the polymerizable compound involved in the polymerization reaction in the cured product to the mass of the polymerizable compound constituting the acrylic resin composition.

[0018] Conventional Tg-less epoxy resins are considered to proceed, for example, by an anionic polymerization mechanism using potassium carboxylate as an initiator. In that case, since the growth end of the polymerization intermediate is stable and highly reactive, there is a characteristic that chain transfer is unlikely to occur. Therefore, it is presumed that network formation with a high crosslink density occurs, and as a result, the modulus retention rate R increases (i.e., becomes Tg-less).

[0019] On the other hand, since the acrylic resin composition has an acrylic compound as the main component of the polymerizable compound, the polymerization mechanism is generally radical polymerization, and it is considered that a considerable amount of chain transfer cannot be avoided. Therefore, it has been considered that network formation with a high crosslink density cannot be expected, and the possibility of becoming Tg-less is low.

[0020] However, in reality, it has been found that even when an acrylic resin composition in which an acrylic compound is the main component of the polymerizable compound is used, the elastic modulus retention rate R of the cured product may be 20% or more and become Tg-less.

[0021] It is possible to obtain an acrylic resin composition in which the elastic modulus retention rate R of the cured product is 20% or more (preferably, the elastic modulus retention rate R is 30% or more) by using various acrylic compounds. The corrected pre-Tg-less index Y of the polymerizable compound of such an acrylic resin composition is, for example, 170 or less, and may be 160 or less. The corrected pre-Tg-less index Y may also be 90 or more, or 100 or more.

[0022] The corrected pre-Tg-less index Y is represented by Y = ΣCi / Σ{Ci·(Nfi - 1) / MRi}.

[0023] Ci is the mass ratio of N kinds of monomers mi, and ΣCi may be 1, or ΣCi may not be 1 in each calculation formula.

[0024] Nfi is the number of functional groups having a radical-polymerizable carbon-carbon double bond (hereinafter, also simply referred to as a functional group) present in one molecule of the monomer mi.

[0025] MRi is a value obtained by subtracting the formula weight of only the cyclic skeleton part from the formula weight Mi of the monomer mi. Hereinafter, MRi is also referred to as the "relaxation effective molecular weight". Here, the cyclic skeleton part refers to a ring structure other than an aliphatic ring without a crosslinked ring. An aliphatic ring having a crosslinked ring is included in the cyclic skeleton part.

[0026] In other words, the relaxed effective molecular weight is the formula weight of monomer mi excluding ring structures other than aliphatic rings without crosslinking rings. Monomer mi may or may not contain ring structures other than aliphatic rings without crosslinking rings. If the formula weight of monomer mi containing ring structures other than aliphatic rings without crosslinking rings is Mi, then MRi is the formula weight Mi minus the formula weight of the ring structures other than aliphatic rings without crosslinking rings. If the formula weight of monomer mi not containing ring structures other than aliphatic rings without crosslinking rings is Mi, then the formula weight Mi = MRi. When calculating the formula weight of ring structures other than aliphatic rings without crosslinking rings, hydrogen atoms and carbonyl oxygen directly bonded to that ring structure are included in the ring structure, but alkyl groups are not.

[0027] Here, ring structures other than aliphatic rings without bridging rings are rigid and do not have a relaxing effect. Even if the bonds directly connected to such ring structures rotate around the bond axis, that rotation does not contribute to stress relaxation of the network. Aliphatic rings without bridging rings refer to aliphatic rings that contribute to stress relaxation, such as cyclohexane, and do not include aliphatic rings with a bicyclo structure, such as norbornane. In other words, ring structures other than aliphatic rings without bridging rings refer to aromatic rings such as benzene rings and naphthalene rings, their quinones such as benzoquinone rings and naphthoquinone rings, heterocycles such as oxazoline rings, oxazolidone rings, oxazolidinone rings, triazine rings, and triazinetrione rings, and aliphatic rings with bridging rings such as dicyclopentadiene rings and norbornane rings, while saturated aliphatic rings such as cyclohexane rings are excluded. For example, if the formula weight of monomer mi having a cyclohexane ring is Mi, then MRi of that monomer mi is Mi.

[0028] The pre-correction Tg reduction index Y of the coincidence compound reflects the value (MRi / (Nfi - 1)) obtained by dividing MRi of the monomer mi by Nfi - 1. Nfi - 1 is the number of functional groups having radical-polymerizable carbon-carbon double bonds (crosslink-forming functional groups) involved in the crosslink formation of the polymerizable compound. The functional group can be, for example, a (meth)acryloyloxy group or a (meth)acryloyl group. The polymerizable compound (monomer mi) has one functional group not involved in crosslink formation (that is, a functional group consumed for linear polymerization). In other words, the monomer mi having only one functional group does not crosslink and forms a linear polymer. In the case of the monomer mi having Nfi (where 1 < N) functional groups, Nfi - 1 functional groups are involved in crosslink formation. MRi / (Nfi - 1) is an index indicating the degree of crosslinking of the molecular chains contributing to the stress relaxation of the network after curing. The smaller this value, the easier it is for Tg to decrease.

[0029] When the polymerizable compound is a mixture of N types of monomers mi (1 ≤ i ≤ N), the average value (average relaxation effective molecular weight) MRA of MRi is obtained by MRA = Σ(MRi·Ci / Mi) / Σ(Ci / Mi). MRA is calculated by multiplying MRi of each component by the number of that component, adding them up, and dividing by the total number. However, since Ci is not the number but the mass ratio, divide Ci by Mi to obtain the equivalent amount in terms of the number, multiply the equivalent amount in terms of the number by MRi, add up the amounts, calculate the total amount, and divide the total amount by the total number of the equivalent amounts in terms of the number.

[0030] The average value of MRi / (Nfi - 1) is ΣCi / Σ{Ci·(Nfi - 1) / MRi}, and this is the pre-correction Tg reduction index Y. Y is a rough index as to whether the polymerizable compound undergoes Tg reduction. The value obtained by dividing the average relaxation effective molecular weight by the pre-correction Tg reduction index Y is the average value of Nfi - 1 (average crosslink-forming functional group number).

[0031] Basically, the larger the MRi of the monomer mi constituting the polymerizable compound, the greater the stress relaxation effect, and the easier it is for the cured product to transition from a glassy state to a rubbery state when heated. On the other hand, the larger the number of crosslinking functional groups Nfi-1, the smaller the relaxation effect, and the more difficult it is for the cured product to transition from a glassy state to a rubbery state when heated. When the pre-correction Tg-less index Y is 170 or less, Nfi-1 is sufficiently large relative to MRi, so the cured product is likely to become Tg-less. Also, when the pre-correction Tg-less index Y is 90 or higher, the cured product is likely to exhibit higher mechanical strength.

[0032] When monomers with very high MRi / (Nfi-1) and monomers with very low MRi / (Nfi-1) are mixed, the variability of the average value Y increases. In this case, the average value Y of MRi / (Nfi-1) no longer reflects the stress relaxation effect of the long chain of monomers with high MRi / (Nfi-1). On the other hand, the corrected Tg-less index Z, corrected by Z=Y·v, is less affected by such variability and therefore serves as a more accurate indicator of Tg-lessness.

[0033] Here, v is v = {Σ(Ti 2 )·(Ci / Mi) / Σ(Ci / Mi)} 1 / 2 It is expressed as / {Σ(Ti·Ci / Mi) / Σ(Ci / Mi)}, where Ti = MRi / (Nfi-1).

[0034] The corrected Tg-less index Z is preferably, for example, 100 ≤ Z ≤ 170. When Z is 100 or higher, the crosslinking density becomes low enough to sufficiently suppress the shrinkage stress of the cured product, making the cured product less susceptible to damage. On the other hand, when Z is 170 or lower, the crosslinking density becomes moderately high, the thermal motion of the network is more easily constrained, and Tg-less is more likely to occur.

[0035] Furthermore, it is desirable that the high-temperature stability index X of the polymerizable compound satisfies 10 ≤ X. X is given by X = (HL) × 1000.

[0036] H is given by H=[Σ{Qi·(Nfi-1)·Ci / Mi}] / ΣCi. Qi is the amount obtained by subtracting the formula weight of the side chains attached to the ring (including the carbonyl oxygen directly attached to the ring) from the formula weight of only the cyclic skeleton portion of monomer mi. However, the formula weight of the cyclic aliphatic portion is multiplied by 0.5. Qi is one of the indicators for estimating the heat resistance of monomer mi and indicates the extent to which the formula weight of the cyclic skeleton is included. If the cyclic skeleton portion is a cyclic aliphatic portion, the heat resistance will be lower compared to aromatic rings, etc. Empirically, multiplying the formula weight of the cyclic aliphatic portion by 1 / 2 brings it in line with the actual substance. Note that "carbonyl oxygen directly attached to the ring" refers to, for example, the oxygen of the carbonyl group that constitutes the ring, such as an isocyanurate ring.

[0037] L is represented by L=[Σ{(Pi / Nfi)·(Ci / Mi)}] / ΣCi. Pi is the amount obtained by subtracting the formula weights of the (meth)acryloyloxy group and the cyclic skeleton from the formula weight Mi of the monomer mi, adding the formula weight of the radically polymerizable carbon-carbon double bond, and then subtracting the formula weights of the side chains that do not participate in the post-polymerization network, and the formula weights of the heteroatoms (O, N, S, etc.) directly attached to the aromatic rings that constitute the main chain. Examples of side chains that do not participate in the post-polymerization network include the ethyl group (-CH2-CH3) on the right side of A-TMPTA (see Table 1A) described later, and the two methyl groups (-CH3) in the central side chain of light acrylate NP-A (see Table 1A). These groups do not participate in network formation, and even if they are cleaved at high temperatures, the network structure is maintained. The formula weight of the carbon-carbon double bond portion in radical polymerizable compounds is 27 (corresponding to CH2CH) for each functional group in the case of acrylic and styryl groups, and 26 (corresponding to CH2C) for methacrylic groups. These values ​​are added together. Ester bonds are clearly more stable at high temperatures than linear aliphatic hydrocarbon groups, so the formula weight of the ester bond portion OC=O is not added. In the case of maleimide, the carbon-carbon double bond portion constitutes the cyclic skeleton, so it is not added at all.

[0038] The high-temperature stability index X represents the ability of the cured network to withstand thermal decomposition at high temperatures (e.g., around 300°C) and maintain its chemical structure. If X is 10 or higher, the heat resistance is sufficiently high, the network is maintained even at high temperatures, and cracking is unlikely to occur.

[0039] H is an indicator of the proportion of molecular chains present in the entire system that contribute to the cured product's ability to withstand thermal decomposition at high temperatures and maintain its chemical structure. When multiple monomers mi are mixed, H is calculated by weighting the molecular weight of each monomer component (Qi), which is the molecular weight of the cyclic skeleton excluding the substituents attached to it (= heat-resistant cyclic skeleton molecular weight Qi), with the number of crosslinking functional groups (Nf-1), summing these values ​​for all monomers, and converting them to a value per unit mass.

[0040] L is an index that indicates the proportion of molecular chains in the entire system that could cause the network to collapse if the cured product undergoes thermal decomposition at high temperatures and the bonds are broken. When multiple monomers mi are mixed, L is calculated by dividing the formula weight of the portion that forms carbon-carbon bonds when vinyl polymerization occurs, the formula weight of the acyclic chains originally present in the monomer skeleton excluding side chains that do not participate in network formation, and the formula weight of the heteroatoms (O, N, S) directly attached to the aromatic ring and participating in network formation (= low thermal stability bond molecular weight Pi) by the number of functional groups Nf for each monomer, summing these values ​​for all monomers, and converting them to a value per unit mass. The reason for dividing by the number of functional groups Nf is that, in the case of polyfunctional compounds, even if one site is broken by thermal decomposition, the chemical structure of the network can be maintained as long as other routes are not broken.

[0041] Unlike thermosetting resins such as epoxy resins, acrylic resin compositions undergo polymerization reactions even at low temperatures. The curing temperature of acrylic resin compositions can be arbitrarily controlled by the activation temperature of the curing agent.

[0042] For example, a thermal polymerization initiator may be used as the curing agent. The thermal polymerization initiator may be used in combination with a reducing agent that promotes polymerization. A thermal polymerization initiator is a curing agent that is activated by heating to promote the polymerization of polymerizable compounds. Activation refers to, for example, decomposition to generate radicals. The activation temperature of the curing agent or thermal polymerization initiator may be 100°C or lower, 90°C or lower, or 80°C or lower. By using such a curing agent, an acrylic resin composition that cures at low temperatures of 100°C or lower, 90°C or lower, or 80°C or lower can be obtained. The activation temperature of the curing agent may be 100°C or lower by combining a thermal polymerization initiator with a reducing agent that has a high activation temperature exceeding 100°C. The reducing agent may be a material that reacts with the thermal polymerization initiator to generate radicals.

[0043] Examples of thermal polymerization initiators that can be used include azo polymerization initiators, peroxide polymerization initiators, and redox polymerization initiators.

[0044] Examples of azo polymerization initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2-methylpropionic acid)dimethyl, 4,4'-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2'-azobis(2-amidinopropane)dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis(2-methylpropionamidine)disulfate, and 2,2'-azobis(N,N'-dimethyleneisobutylamidine)dihydrochloride.

[0045] Examples of peroxide-based polymerization initiators include cumene hydroperoxide, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, stearoyl peroxide, o-chlorobenzoyl peroxide, acetyl peroxide, t-butyl hydroperoxide, t-butyl peroxyacetate, t-butyl peroxyisobutyrate, 3,5,5-trimethylhexanoyl peroxide, t-butyl peroxy-2-ethylhexanoate, di-t-butyl peroxide, t-butyl permaleate, dicumyl peroxide, and methyl ethyl ketone peroxide.

[0046] Examples of reducing agents include tertiary amines, thiourea derivatives, and transition metal salts. The reducing agent may be used individually or in combination of two or more.

[0047] Examples of tertiary amines include triethylamine, tripropylamine, tributylamine, and N,N-dimethylparatoluidine. Examples of thiourea derivatives include 2-mercaptobenzimidazole, methylthiourea, dibutylthiourea, ethylenethiourea, acetyl-2-thiourea, benzoylthiourea, N,N-diphenylthiourea, N,N-diethylthiourea, N,N-dibutylthiourea, and tetramethylthiourea. Among thiourea derivatives, ethylenethiourea is preferred. Examples of transition metal salts include naphthenic acid transition metal salts (cobalt naphthenate, manganese naphthenate, copper naphthenate, etc.) and vanadylacetylacetonate. Among transition metal salts, naphthenic acid transition metal salts are preferred.

[0048] There are no particular restrictions on the amount of curing agent used, but for example, it may be in the range of 0.01 to 5 parts by mass, preferably 0.05 to 3 parts by mass, per 100 parts by mass of polymerizable compound. The curing agent may be used alone or in combination of two or more types.

[0049] Unlike thermosetting resins such as epoxy resins, acrylic resin compositions have low viscosity and a fast polymerization reaction rate. In the case of epoxy resins, obtaining polyfunctional monomers inevitably increases the molecular weight, and consequently, they often remain amorphous and solid at room temperature. Such epoxy resins tend to become highly viscous even when heated to liquefy. On the other hand, with acrylic compounds, it is easy to obtain polyfunctional monomers (monomer mi) that exhibit a low viscosity liquid state at room temperature. Highly symmetrical monomers with a ring structure (for example, tris(2-acryloyloxyethyl) isocyanurate) crystallize and become solid at room temperature, but by moderately heating them to melt them or mixing them with other monomers to inhibit crystallization, very low viscosity acrylic resin compositions can be easily obtained.

[0050] Using a B-type viscometer, the viscosity of the polymerizable compound or acrylic resin composition before mixing with the curing agent, measured at 25°C, is, for example, 1000 mPa·s or less, preferably 800 mPa·s or less. The higher the curing temperature of the acrylic resin composition, the lower the viscosity of the acrylic resin composition at the curing temperature, making it easier to handle and accelerating the polymerization reaction. Therefore, the curing temperature of the acrylic resin composition is preferably 40°C or higher, or 50°C or higher, and may also be 60°C or higher. Considering the thermal stability at room temperature, the curing temperature may be 70°C or higher. When redox polymerization is performed using a reducing agent, the reaction proceeds gradually at room temperature, so the acrylic resin composition may be cured and gelled at a temperature that does not cause the reaction to proceed rapidly (e.g., 40°C or lower) for a period of, for example, 1 hour to 20 hours. After exceeding the gelation point, it is preferable to further raise the temperature of the gel to about 80°C and cure it.

[0051] The average formula weight of the polymerizable compound may be, for example, 290 or more and 600 or less. The average formula weight of a polymerizable compound containing N-type (1≦N) monomer mi (1≦i≦N) is ΣCi / (ΣCi / Mi). When the average formula weight of the polymerizable compound is 600 or less, the viscosity of the acrylic resin composition becomes sufficiently low, which is advantageous in terms of the handling of the acrylic resin composition. The average formula weight of the polymerizable compound may also be 300 or more and 500 or less.

[0052] The polymerizable compound may contain at least one Class 1 monomer having a ring structure other than an aliphatic ring without a crosslinking ring and two or more (meth)acryloyloxy groups. Cured products of acrylic resin compositions containing Class 1 monomers tend to have suppressed relaxation when heated and tend to be Tg-less.

[0053] The polymerizable compound preferably contains 20% by mass or more of Class 1 monomers, may contain 30% by mass or more, or may contain 50% by mass or more.

[0054] It is desirable that at least one of the Class 1 monomers has three or more (meth)acryloyloxy groups. In this case, the cured product of the acrylic resin composition is more likely to be Tg-less. It is particularly desirable that the Class 1 monomer has three (meth)acryloyloxy groups. The polymerizable compound is preferably 30% by mass or more of the Class 1 monomer having three or more (preferably three) (meth)acryloyloxy groups, may be 40% by mass or more, or 50% by mass or more.

[0055] At least one of the Class 1 monomers may have a triazinetrione ring as a non-aliphatic ring structure without a crosslinking ring. In this case, the cured product of the acrylic resin composition is more likely to be Tg-less. The polymerizable compound preferably contains 30% by mass or more of the Class 1 monomer having a triazinetrione ring, may contain 40% by mass or more, or may contain 50% by mass or more.

[0056] Other than the triazinetrione ring, examples of non-aliphatic ring structures without a crosslinking ring include the triazine ring, benzene ring, naphthalene ring, benzoquinone ring, norbornane ring, and dicyclopentadiene ring. At least some of the Class 1 monomers may have these ring structures.

[0057] The formula weight of the Class 1 monomer is, for example, 400 or more. The formula weight of the Class 1 monomer may also be, for example, 500 or less.

[0058] Specific examples of Class 1 monomers include tris(2-acryloyloxyethyl) isocyanurate, acrylic acid adducts of bisphenol A diglycidyl ether, and dimethylol tricyclodecanediaacrylate. Examples of Class 1 monomers are shown below in structural formulas.

[0059] [ka]

[0060] [ka]

[0061] [ka]

[0062] The polymerizable compound may further contain at least one Class II monomer that does not have a ring structure other than an aliphatic ring without a crosslinking ring, and has two or more (meth)acryloyloxy groups. Acrylic resin compositions containing Class II monomers have relatively low viscosity and are excellent in terms of handling and polymerization reaction rate. The polymerizable compound preferably contains 30% by mass or more of Class II monomers, and may contain 40% by mass or more.

[0063] The formula weight of the Class 2 monomer is, for example, 280 or more. The formula weight of the Class 2 monomer may be, for example, 600 or less (or 400 or less).

[0064] At least one of the Class II monomers may have an aliphatic ring without a crosslinking ring and two or more (meth)acryloyloxy groups. The aliphatic ring may be a cyclohexane ring.

[0065] At least one of the Class II monomers may have three or more (meth)acryloyloxy groups. Such Class II monomers do not have a ring structure.

[0066] Examples of Class 2 monomers are shown below in structural formulas.

[0067] [ka]

[0068] [ka]

[0069] In addition to the above, the acrylic resin composition may contain various monomers and oligomers having (meth)acryloyl groups. Examples of monomers include (meth)acrylic acid esters of hydroxy compounds, adducts obtained by adding (meth)acrylic acid to epoxy compounds, acid amides of nitrogen-containing compounds and (meth)acrylic acid, and (meth)acrylic acid. Examples of oligomers include (meth)acrylates of oligomeric polyhydroxy compounds and (meth)acrylates of oligomeric epoxy compounds. However, it is desirable that the polymerizable compound contains 80% by mass or more in total of Class 1 monomers and Class 2 monomers, and may contain 90% by mass or more, 95% by mass or more, or 99% by mass or more.

[0070] The acrylic resin composition may contain additives in addition to polymerizable compounds and curing agents, as needed. Examples of additives include polymerization inhibitors, thickeners, UV absorbers, antioxidants, toughness modifiers, plasticizers, catalysts, reaction accelerators, coupling agents, colorants, wettability modifiers, wetting agents, leveling agents, defoamers, and fillers (inorganic particles, resin particles, etc.).

[0071] Examples of polymerization inhibitors include hydroquinone, t-butylhydroquinone, methylhydroquinone, 1,4-benzoquinone, 2-t-butyl-1,4-benzoquinone, t-butylcatechol, 2,6-di-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, methoxyphenol, 6-t-butyl-2,4-xylenol, phenothiazine, copper(II) dibutyldithiocarbamate, and 1,1-diphenyl-2-picrylhydrazyl free radical.

[0072] Next, one application of the acrylic resin composition according to the present invention will be described. The acrylic resin composition that produces a Tg-less cured product is useful as a building panel material containing a Tg-less material. Building panel materials are required to exhibit sufficient load-bearing capacity even at high temperatures during a fire. Since Tg-less materials can maintain a high storage modulus even at high temperatures, they exhibit sufficient load-bearing capacity during a fire.

[0073] The Tg-less material may be fiber-reinforced plastic (FRP). That is, the Tg-less material may contain fibers and an acrylic resin composition impregnated into the fibers. The acrylic resin composition has low viscosity and excellent fluidity, so it can be easily impregnated into the fibers. Furthermore, the acrylic resin composition hardens rapidly at low temperatures, so no special heating equipment is required. For this reason, the Tg-less material containing the acrylic resin composition is suitable for forming large building panel materials and is also suitable for continuous molding.

[0074] In Tg-less materials, the acrylic resin composition may be in a cured state or an uncured state. If the acrylic resin composition is uncured, the acrylic resin composition should be cured before using the Tg-less material.

[0075] Fibers may be included in the Tg-less material in the form of fiber aggregates. Examples of fiber aggregates include tows and sheet-like aggregates. Examples of sheet-like aggregates include unidirectional laminates, multiaxial laminates, woven fabrics, nonwoven fabrics, knitted fabrics, and braided fabrics. The fiber length and fiber diameter can be selected according to the required properties of the Tg-less material.

[0076] The fibers may be either organic or inorganic, or a combination of both. Examples of organic fibers include resin fibers (aramid fibers, para-aramid fibers, high-strength polyethylene resin, ultra-high molecular weight polyethylene fibers, high-strength polyarylate fibers, poly(para-phenylene)-benzobis-oxazole fibers, etc.). Examples of inorganic fibers include carbon fibers, graphite fibers, basalt fibers, silicon carbide fibers, alumina fibers, boron fibers, tungsten-carbide fibers, glass fibers, and mineral fibers. The fibers may be surface-treated as needed. These fibers may be used individually or in combination of two or more types. Considering the balance between cost and fire resistance, at least one fiber selected from the group consisting of glass fibers, basalt fibers, and carbon fibers may be used.

[0077] The fiber content in the Tg-less material is not particularly limited, but may be 20% or more by volume and 70% or less by volume, or 30% or more by volume and 60% or less by volume.

[0078] Figure 1 is a schematic structural diagram of an example of a building panel material containing a Tg-less material. The panel material 100 comprises a two-dimensionally extending frame material 20, a core material 30 filled in the gaps of the frame material, a pair of skin layers 40 sandwiching the frame material 20 and the core material 30, and a fire-resistant coating material 50 covering the surface of the skin layers 40. The Tg-less material is included as FRP in at least one of the frame material 20 and the skin layers 40. In order to maintain high load-bearing capacity even at temperatures reached during a fire, it is desirable to include the Tg-less material (FRP) in both the frame material 20 and the skin layers 40.

[0079] The skeletal structure 20 is formed of FRP ribs arranged in a mesh or honeycomb pattern. The core material 30 is, for example, a lightweight foam material with thermal insulation properties. The skin layer 40 is an FRP sheet, and the skeletal structure 20 and the core material 30 are sandwiched between a pair of sheets. When the fire-resistant coating material 50 is directly exposed to flames during a fire, it does not burn but expands to form a thermal insulation layer. In such a structure, the skin layer 40 is protected from direct exposure to flames. Therefore, non-combustibility is not required for the skin layer 40. The temperature of the skin layer 40 reached during a fire is assumed to be 200°C or less.

[0080] The following is a summary of the terms used. (1) Number of functional groups Nf: The number of functional groups contained in one molecule of radical polymerizable monomer. (2) Formula weight M: Molecular weight of the radical polymerizable monomer. (3) Acyclic aliphatic skeleton molecular weight: The amount obtained by subtracting the molecular weight of the (meth)acryloyloxy group and the cyclic skeleton from the formula weight M. (4) Acyclic aliphatic chain molecular weight: The amount obtained by adding the molecular weight of the radical-reactive carbon double bond to the molecular weight of the acyclic aliphatic skeleton (3). In the case of acrylic and styryl groups, 27, corresponding to CH2CH, is added for each functional group, and in the case of methacrylic groups, 26, corresponding to CH2C, is added. The molecular weight of the ester bond portion OC=O is not added. In the case of maleimide, polymerizable double bonds also constitute the cyclic skeleton, so they are not added at all. (5) Low thermal stability bond molecular weight P: The amount obtained by subtracting the molecular weight of the side chains that do not participate in network formation after polymerization, and the molecular weight of the heteroatoms (O, N, S) that are directly attached to the aromatic ring and constitute the main chain, from the molecular weight of the acyclic aliphatic chain (4).

[0081] (6) Molecular weight of the cyclic skeleton: The molecular weight of only the cyclic skeleton portion. (7) Heat-resistant cyclic skeleton molecular weight Q: The amount obtained by subtracting the molecular weight of the side chains attached to the ring from the molecular weight of the cyclic skeleton (6). The molecular weight of the oxygen in the carbonyl group constituting the ring, such as the isocyanurate ring, is also excluded. In addition, the molecular weight of the cyclic aliphatic portion is multiplied by 0.5. (8) Relaxation effective molecular weight MR: The molecular weight of the portion that can contribute to stress relaxation of the network after hardening. The bonds that make up the cyclic skeleton do not contribute to stress relaxation of the network even when they rotate around the axis, so they are subtracted from the formula weight. This is the amount obtained by subtracting the molecular weight of the cyclic skeleton portion only (6) from the formula weight (2). (9) Functional group equivalent: Mfeq = M / Nf. The mass of a radical polymerizable monomer having one functional group. This is the amount obtained by dividing the formula weight M by the number of functional groups Nf. (10) Equivalent of crosslinking functional groups: Mceq = M / (Nf-1). Of the functional groups of a radical polymerizable monomer, one is consumed for linear polymerization, and the other functional groups are consumed for crosslinking. Therefore, the equivalent of crosslinking functional groups is obtained by dividing the formula weight M by the number of functional groups Nf minus 1.

[0082] (11) Relaxation effective molecular weight / Number of crosslinking functional groups: T = MR / (Nf-1). This is an indicator of the extent to which molecular chains contributing to stress relaxation of the network after hardening are crosslinked. It can be calculated by dividing the relaxation effective molecular weight MR by the number of crosslinking functional groups (i.e., the number of functional groups Nf-1). A smaller value of this is advantageous for reducing Tg. (12) Average functional group equivalent: The average value of the functional group equivalent when multiple radical polymerizable monomers are mixed. If Ci is the mass ratio of each monomer, it can be calculated as ΣCi / Σ(Ci / Mfeqi). (13) Average equivalent of crosslinking functional groups: The average value of the equivalent of crosslinking functional groups when multiple radical polymerizable monomers are mixed. It is calculated as ΣCi / Σ(Ci / Mceqi). (14) Mean Relaxation Effective Molecular Weight: The amount obtained by dividing the total mass of relaxation effective molecules present in the system by the number of moles present in the system. It can be calculated as Σ(MRi·Ci / Mi) / Σ(Ci / Mi). (15) The average value of the pre-corrected Tg-less index Y = {relaxing effective molecular weight / number of crosslinking functional groups}. Relaxing effective molecular weight / number of crosslinking functional groups = average value of T. If the mass ratio of each monomer is Ci, it can be calculated as ΣCi / Σ(Ci / Ti), that is, ΣCi / Σ{Ci·(Nfi-1) / MRi}. Basically, this value is an indicator of Tg-lessness.

[0083] (16) Average number of crosslinking functional groups = Average relaxed effective molecular weight / Pre-corrected Tg-less index Y. The average value of the number of crosslinking functional groups when multiple radical polymerizable monomers are mixed. It is obtained by dividing the average relaxed effective molecular weight (14) by the pre-corrected Tg-less index Y. (17) Variability correction coefficient v = Root mean square / Arithmetic mean. This value is calculated to show how much variation there is in the relaxation effective molecular weight / number of crosslinking functional groups of each monomer component when multiple radical polymerizable monomers are mixed. {Σ(Ti) 2 ·(Ci / Mi) / Σ(Ci / Mi)} 1 / 2 It can be calculated using / {Σ(Ti·Ci / Mi) / Σ(Ci / Mi)}. (18) Corrected Tg-less index Z: A value obtained by correcting Y by multiplying the uncorrected Tg-less index Y by a variation correction coefficient v. When the average value is low Y due to a mixture of monomers with high T values ​​and monomers with low T values, the variation is considered large, and if evaluation is done solely by the average value of the T values ​​of each monomer component, the stress relaxation effect of the long chain with high T values ​​will be ignored, so variation correction is performed. 100 ≤ Z ≤ 170 is preferred. (19) Connectivity Heat-Resistant Cyclic Skeleton Index H: An index indicating the proportion of molecular chains present in the entire system that can contribute to the cured product withstanding thermal decomposition at high temperatures (e.g., around 300°C) and maintaining its chemical structure. (20) Low thermal stability bond index L: An index that indicates the proportion of molecular chains in the entire system that could cause the network to collapse if the cured product undergoes thermal decomposition at high temperatures (e.g., around 300°C) and its bonds are broken. (21) High-temperature stability index X = (Heat-resistant cyclic skeleton index - Low-temperature stability bond index) × 1000 = (HL) × 1000: An index representing the ability of the cured network to withstand thermal decomposition at high temperatures (e.g., around 300°C) and maintain its chemical structure. 10 ≤ X is preferred.

[0084] [Examples] The present invention will be described in detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0085] Examples 1-7 and Comparative Examples 1-8 (1) Preparation of acrylic resin composition The components shown in Table 1A (each component's parameter is shown in Table 1B) were mixed in the mass ratios shown in Tables 2 and 3, and a homogeneous liquid polymerizable compound mixture was prepared at room temperature while stirring. The meaning of the parameters or indices No. 12 to No. 21 in Tables 2 and 3 is shown in Table 4.

[0086] Table 2 shows the breakdown of A-9300 and phenylmaleimide (PMI) in the adduct of Example 5, indicated by the values ​​marked with an asterisk (*). Since PMI has a vinyl polymerizable double bond incorporated into its ring structure, this specification calculates the values ​​in each table assuming that the total amount of PMI forms an adduct with A-9300 in a molar ratio of 1:1. In other words, although Example 5 is actually a mixed formulation of three components: A-9300, DCP-A, and PMI, the calculations are performed assuming a mixed formulation of two components: the above adduct and DCP-A. Note that the same method can be used for calculations when a vinyl polymerizable double bond is incorporated into the ring structure, not limited to PMI.

[0087] Subsequently, to 100 parts by mass of a polymerizable compound mixture, 1 part by mass of methyl ethyl ketone peroxide and 1 part by mass of cobalt naphthenate with a cobalt content of 8% by mass were added as curing agents, and 1 part by mass of 2-ethylhexanoic acid was added as a curing agent to prepare a curable acrylic resin composition that can be activated even at room temperature.

[0088] (2) Evaluation <High-temperature crack resistance> The acrylic resin composition obtained in (1) above was cured overnight at 40°C, then heated at 80°C for 1 hour to obtain a cured product. The obtained cured product was kept at room temperature for 16 hours, then heated at 80°C for 1 hour, and further heated at 200°C for 1 hour. After that, the temperature of the cured product was raised to 275°C over 20 minutes, and immediately thereafter cooled to room temperature. It was evaluated according to the following criteria. The results are shown in Tables 2 and 3. ○: No cracks △: Slight cracks have occurred. ×: Significant cracking has occurred.

[0089] <Maintenance of elastic modulus R> The storage modulus of the cured material at 25°C and 250°C was measured using a DMA measuring device (Hitachi High-Tech Science Corporation, DMS6100) by heating from 20°C to 320°C at a frequency of 1 Hz and a heating rate of 2°C / min. The curing rate of the cured material was approximately 100%. The ratio of the storage modulus at 250°C to the storage modulus at 25°C was calculated as the modulus retention rate R. The results are shown in Tables 2 and 3. Tables 2 and 3 indicate ○ when R is 20% or more, and × when R is less than 20%.

[0090] [Table 1A]

[0091] [Table 1B]

[0092] [Table 2]

[0093] [Table 3]

[0094] [Table 4]

[0095] It can be seen that the cured products of each example exhibit excellent high-temperature crack resistance and are effectively Tg-less cured products with an elastic modulus retention rate R of 20% or more, and even 30% or more. Furthermore, it can be seen that in each example, the pre-correction Tg-less index Y is 90 to 170, the corrected Tg-less index Z is 100 to 170, and the high-temperature stability index X is 10 or more, whereas in the comparative example, one or more of these values ​​fall outside the above range. [Industrial applicability]

[0096] The acrylic resin composition according to the present invention can be used in various applications where mechanical strength at high temperatures is required, and is useful, for example, as a building panel material.

Explanation of reference numerals

[0097] 20: Skeletal material 30: Core material 40: Skin layer 50: Fireproof coating material 100: Building panel material

Claims

1. A building panel material containing Tg-less material, The Tg-less material comprises fibers and an acrylic resin composition impregnated into the fibers. The acrylic resin composition comprises a polymerizable compound containing one or more monomers mi (1 ≤ i ≤ N) and a curing agent. i is a coefficient that distinguishes the monomer mi, and is an integer between 1 and N, The uncorrected Tg-less index Y of the polymerizable compound is 170 or less. Y is shown as Y = ΣCi / Σ{Ci・(Nfi-1) / MRi}, Ci is the mass ratio of the monomer mi, Nfi is the number of radically polymerizable carbon-carbon double bond functional groups present in one molecule of the monomer mi, MRi is the value obtained by subtracting the formula weight of only the cyclic skeleton portion from the formula weight Mi of the monomer mi. The polymerizable compound comprises at least one Class I monomer having a ring structure other than an aliphatic ring without a crosslinking ring and two or more (meth)acryloyloxy groups, At least one of the Class 1 monomers has three or more (meth)acryloyloxy groups, The content of the Class 1 monomer in the polymerizable compound is 20% by mass or more. A cured product is produced in which the ratio of the storage modulus at 250°C to the storage modulus at 25°C is 20% or more. The storage modulus is measured using a cured product with a hardening rate of 95% or more, by heating it from -50°C to +350°C using a DMA measuring device at a frequency of 1 Hz and a heating rate of 2°C / min, for building panel materials.

2. The corrected Tg-less index Z of the polymerizable compound satisfies 100 ≤ Z ≤ 170. It is shown that Z = Y・v, v={Σ(Ti2)・(Ci / Mi) / Σ(Ci / Mi)}1 / 2 / {Σ(Ti・Ci / Mi) / Σ(Ci / Mi)}, The building panel material according to claim 1, wherein Ti = MRi / (Nfi-1).

3. The high-temperature stability index X of the polymerizable compound is 10 ≤ X, X is shown as (H - L) × 1000, H is shown as [Σ{Qi・(Nfi-1)・Ci / Mi}] / ΣCi, It is shown that L = [Σ{(Pi / Nfi)・(Ci / Mi)}] / ΣCi, Qi is the amount obtained by subtracting the formula weight of the side chains attached to the ring (including the carbonyl oxygen directly attached to the ring) from the formula weight of only the cyclic skeleton portion of monomer mi (however, if the cyclic skeleton portion is a cyclic aliphatic portion, multiply by 0.5). The building panel material according to claim 1 or 2, wherein Pi is the amount obtained by subtracting the formula weights of the (meth)acryloyloxy group and the cyclic skeleton portion from the formula weight Mi of the monomer mi, adding the formula weight of the radically polymerizable carbon-carbon double bond portion, and then subtracting the formula weights of the side chains that do not participate in the network after polymerization and the formula weights of the heteroatoms directly connected to the aromatic rings constituting the main chain.

4. The building panel material according to any one of claims 1 to 3, wherein the activation temperature of the curing agent is 100°C or lower.

5. A building panel material according to any one of claims 1 to 4, wherein the viscosity of the polymerizable compound, as measured at a temperature of 50°C using a B-type viscometer, is 1000 mPa·s or less.

6. The building panel material according to any one of claims 1 to 5, wherein the average value of the formula weight ΣCi / (ΣCi / Mi) of the polymerizable compound is 290 or more and 600 or less.

7. The building panel material according to any one of claims 1 to 6, wherein at least one of the Class 1 monomers has a triazinetrione ring as a ring structure other than the aliphatic ring without the crosslinking ring.

8. The building panel material according to any one of claims 1 to 7, wherein the formula weight of the Class 1 monomer is 400 or more.

9. The polymerizable compound further comprises at least one Class II monomer having no ring structure other than an aliphatic ring without a crosslinking ring, and having two or more (meth)acryloyloxy groups, according to any one of claims 1 to 8.

10. The building panel material according to claim 9, wherein the formula weight of the Class II monomer is 280 or more.

11. The building panel material according to claim 9 or 10, wherein at least one of the Class II monomers has an aliphatic ring without a crosslinking ring and two or more (meth)acryloyloxy groups.

12. The building panel material according to any one of claims 9 to 11, wherein at least one of the Class II monomers has three or more (meth)acryloyloxy groups.

13. A building panel material containing Tg-less material, The Tg-less material comprises fibers and an acrylic resin composition impregnated into the fibers. The acrylic resin composition comprises a polymerizable compound containing one or more monomers mi (1 ≤ i ≤ N) and a curing agent. i is a coefficient that distinguishes the monomer mi, and is an integer between 1 and N, The polymerizable compound comprises at least one Class I monomer having a ring structure other than an aliphatic ring without a crosslinking ring and two or more (meth)acryloyloxy groups, At least one of the Class 1 monomers has three or more (meth)acryloyloxy groups, The content of the Class 1 monomer in the polymerizable compound is 20% by mass or more. The polymerizable compound further comprises at least one Class II monomer that does not have a ring structure other than an aliphatic ring without the crosslinking ring, and has two or more (meth)acryloyloxy groups. Here are the conditions: (a) The formula weight of the Class II monomer is 280 or more; (b) At least one of the Class II monomers has an aliphatic ring without a crosslinking ring and two or more (meth)acryloyloxy groups; and, (c) At least one of the Class II monomers has three or more (meth)acryloyloxy groups; Satisfying at least one of the following conditions, A cured product is produced in which the ratio of the storage modulus at 250°C to the storage modulus at 25°C is 20% or more. The storage modulus is measured using a cured product with a hardening rate of 95% or more, by heating it from -50°C to +350°C using a DMA measuring device at a frequency of 1 Hz and a heating rate of 2°C / min, for building panel materials.

14. The device comprises a two-dimensionally extending skeletal material, a core material filled in the gaps of the skeletal material, a pair of skin layers sandwiching the skeletal material and the core material, and a fire-resistant coating material covering the surface of the skin layers. A building panel material according to any one of claims 1 to 13, wherein at least one of the skeletal material and the skin layer includes the Tg-less material.

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