Cyanacrylate compositions containing non-hazardous stabilizers

Abstract

The present invention relates to a curable cyanoacrylate composition comprising (i) at least one cyanoacrylate monomer, and (ii) at least one free radical stabilizer, wherein the free radical stabilizer is non-hazardous and shows a good compatibility with the cyanoacrylate without impairing the reactivity of the cyanoacrylate and its properties after curing.

Description

Technical Field

[0001] This invention relates to a curable cyanoacrylate composition comprising (i) at least one cyanoacrylate monomer and (ii) at least one free radical stabilizer of formula (I) as defined below. The free radical stabilizer of formula (I) is non-hazardous and exhibits good compatibility with cyanoacrylate without impairing the reactivity of the cyanoacrylate or its properties after curing. This invention also relates to the use of compounds of formula (I) for inhibiting free radical polymerization in compositions comprising at least one cyanoacrylate monomer. Background Technology

[0002] Cyanoacrylate compositions are well known in the art. In particular, cyanoacrylates represent a class of strong, fast-curing adhesives with industrial, medical, cosmetic, and household applications. Such compositions are sometimes also generally referred to as instant adhesives, powder adhesives, or super adhesives containing monomers having cyanoacrylate groups. The cyanoacrylate groups in the monomers rapidly polymerize in the presence of nucleophiles, such as hydroxyl ions generated from water, to form long, strong chains. Detailed summaries of cyanoacrylate adhesive compositions can be found, for example, in HV Coover, DWDreifus, and JTO'Connor, “Cyanoacrylate Adhesives,” in Handbook of Adhesives, 27, 463-77, edited by I. Skeist, Van Nostrand Reinhold, New York, 3rd edition (1990); or in G. H. Millet, “Cyanoacrylate Adhesives,” in Handbook of Adhesives: Chemistry and Technology, edited by S.R. Hartshorn, Plenum Press, New York, pp. 249-307 (1986).

[0003] Due to the high reactivity of cyanoacrylate groups, cyanoacrylate compositions have a short shelf life. Since cyanoacrylates can also undergo free radical polymerization, cyanoacrylate binders need to be stabilized during storage to prevent free radical instability. Stabilizer systems for cyanoacrylates are well known in the art, such as those disclosed in WO 2019 / 068690. For example, hydroquinone (HQ) is the most commonly used free radical stabilizer in cyanoacrylate compositions. Another commonly used free radical stabilizer in cyanoacrylate compositions is, for example, butylated hydroxyanisole (BHA). Other known suitable free radical stabilizers for cyanoacrylate compositions include, for example, Irganox 1010 (CAS No.: 6683-19-8) or Irganox 1076 (CAS No.: 2082-79-3).

[0004] However, in the EU, for example, HQ is classified as a hazardous substance (signal word "dangerous") and is likely carcinogenic or mutagenic. Furthermore, the US National Institutes of Health reasonably anticipates BHA to be a human carcinogen, and California, for example, lists BHA as a carcinogen. Irganox 1010 is classified as hazardous in at least Canada, and several hazards have been reported, for example, by the European Chemicals Agency (ECHA). The ECHA has also outlined the potential hazards of Irganox 1076. Generally speaking, there are hazard reports for almost every phenolic antioxidant. Although some reports are not fully substantiated, other phenolic antioxidants are considered hazardous based on global, regional, and local regulations / legislation. On the other hand, for those types that have not yet been proven hazardous, there is no known industrial-scale synthesis, meaning no cost-effectiveness requirements have been given.

[0005] Therefore, there is a need in the art for alternative free radical stabilizers in cyanoacrylate compositions. In other words, there is a need for a free radical stabilizer that, on the one hand, is compatible with cyanoacrylates and effectively prevents free radical polymerization in cyanoacrylate compositions, and on the other hand, is, according to existing knowledge, a safe and harmless stabilizer.

[0006] However, cyanoacrylates are fast-curing adhesives on almost all materials, meaning they have a high tendency to polymerize once they come into contact with most materials. Few chemicals are unreactive to cyanoacrylates. For example, over 200 different grades of poly(methyl methacrylate) (PMMA) are commercially available. However, when diluted in cyanoacrylates as a thickener, only a very small number are known to be compatible; all other grades begin to polymerize within minutes to days. As another example regarding possible packaging materials, thousands of grades of polyethylene are commercially available; however, fewer than five of these grades show good compatibility with cyanoacrylates. Therefore, given the specific chemistry and high reactivity involved, it is difficult to find materials compatible with cyanoacrylates, let alone those that perform specific functions such as inhibiting free radical polymerization.

[0007] In view of the above, one object of the present invention is to identify compounds that, on the one hand, are compatible with cyanoacrylates and inhibit free radical polymerization, and on the other hand, are non-hazardous. In particular, one object of the present invention is to identify free radical stabilizers that are not classified as hazardous, are cost-effective, and show good compatibility with cyanoacrylate formulations. Summary of the Invention

[0008] This invention relates to cyanoacrylate compositions comprising a harmless free radical stabilizer. In particular, this invention provides a curable cyanoacrylate composition comprising:

[0009] (i) at least one cyanoacrylate monomer, and

[0010] (ii) at least one free radical stabilizer

[0011] The free radical stabilizer includes one or more compounds of formula (I).

[0012]

[0013] Where (x) represents a double bond and R 3 It does not exist, or (x) represents a single bond and R 3 It can be hydrogen, straight-chain C1-C8 alkyl, branched or cyclic C3-C8 alkyl, straight-chain C1-C8 alkoxy, branched or cyclic C3-C8 alkoxy, straight-chain C2-C8 alkenyl, or branched or cyclic C3-C8 alkenyl;

[0014] R 1 It can be hydrogen, straight-chain C1-C8 alkyl, branched or cyclic C3-C8 alkyl, straight-chain C1-C8 alkoxy, branched or cyclic C3-C8 alkoxy, straight-chain C2-C8 alkenyl, branched or cyclic C3-C8 alkenyl, or the group -C(O)-OR. 2', where R 2 'For linear C1-C 12 Alkyl, branched or cyclic C3-C 12 Alkyl, straight-chain C2-C 12 alkenyl, or branched or cyclic C3-C 12 alkenyl, the straight-chain C1-C 12 Alkyl, branched or cyclic C3-C 12 Alkyl, straight-chain C2-C 12 alkenyl, or branched or cyclic C3-C 12 The alkenyl group may optionally be intercalated with one or more oxygen atoms;

[0015] R 2 For straight chain C1-C 12 Alkyl, branched or cyclic C3-C 12 Alkyl, straight-chain C2-C 12 alkenyl, or branched or cyclic C3-C 12 alkenyl, the straight-chain C1-C 12 Alkyl, branched or cyclic C3-C 12 Alkyl, straight-chain C2-C 12 alkenyl, or branched or cyclic C3-C 12 The alkenyl group may optionally be intercalated with one or more oxygen atoms; R 4 It is hydrogen, straight-chain C1-C8 alkyl, branched or cyclic C3-C8 alkyl, straight-chain C1-C8 alkoxy, branched or cyclic C3-C8 alkoxy, straight-chain C2-C8 alkenyl, or branched or cyclic C3-C8 alkenyl; and R 5 and R 5 'Independently hydrogen or a group -OR 6 , where R 6 Independently hydrogen, straight-chain C1-C8 alkyl, branched or cyclic C3-C8 alkyl, straight-chain C2-C8 alkenyl, or branched or cyclic C3-C8 alkenyl, wherein R 3 Or R 4 One of them and R 1 Together with the carbon atoms they are attached to, they can form 5- to 18-membered saturated or unsaturated rings, which may optionally be interspersed with one or more oxygen atoms; or R 3 and R 4 They can form 5- to 18-membered saturated or unsaturated rings together with the carbon atoms they are attached to, optionally interspersed with one or more oxygen atoms; or R 1 With R 3 and R 4 They can form 5- to 12-membered saturated or unsaturated bicycles together with the carbon atoms to which they are attached, and the bicycles may optionally be interspersed with one or more oxygen atoms.

[0016] The present invention also relates to the use of compounds of formula (I) as defined above for inhibiting free radical polymerization in compositions comprising at least one cyanoacrylate monomer.

[0017] The inventors unexpectedly discovered that conventional free radical stabilizers can be replaced by free radical stabilizers of formula (I), which are currently not classified as hazardous. The non-hazardous free radical stabilizers of formula (I) can be well formulated into cyanoacrylates. Furthermore, the resulting cyanoacrylate compositions achieve similar properties, for example, in terms of shelf life and adhesive properties, compared to prior art compositions containing hazardous stabilizers such as, for example, hydroquinone (HQ) or butylated hydroxyanisole (BHA). Detailed Implementation

[0018] This invention relates to a curable cyanoacrylate composition comprising (i) at least one cyanoacrylate monomer and (ii) at least one free radical stabilizer, wherein the free radical stabilizer comprises one or more compounds of formula (I).

[0019]

[0020] In equation (I) above, (x) represents a double bond or a single bond. In the case of a double bond, R 3 It does not exist. On the other hand, when (x) represents a single bond, R 3 It can be hydrogen, a straight-chain C1-C8 alkyl, a branched or cyclic C3-C8 alkyl, a straight-chain C1-C8 alkoxy, a branched or cyclic C3-C8 alkoxy, a straight-chain C2-C8 alkenyl, or a branched or cyclic C3-C8 alkenyl. Furthermore, when (x) represents a single bond, R... 3 In a preferred embodiment, it is hydrogen, a straight-chain C1-C4 alkyl group, or a branched C3-C4 alkyl group, preferably R. 3 It is hydrogen or methyl, more preferably hydrogen. Alternatively, when (x) is a double bond, as described above, R 3 It does not exist at all.

[0021] R in equation (I) above 1 It can be hydrogen, straight-chain C1-C8 alkyl, branched or cyclic C3-C8 alkyl, straight-chain C1-C8 alkoxy, branched or cyclic C3-C8 alkoxy, straight-chain C2-C8 alkenyl, branched or cyclic C3-C8 alkenyl, or the group -C(O)-OR. 2 '. Group -C(O)-OR 2 R in ' 2 'For linear C1-C 12 Alkyl, branched or cyclic C3-C 12 Alkyl, straight-chain C2-C 12 alkenyl, or branched or cyclic C3-C 12Alkenyl group. R group 2 C1-C in ' 12 Alkyl, branched or cyclic C3-C 12 Alkyl, straight-chain C2-C 12 alkenyl, or branched or cyclic C3-C 12 The alkenyl group may optionally be interspersed with one or more oxygen atoms, such as, for example, one or two oxygen atoms.

[0022] In the preferred embodiment, R 1 The group is -C(O)-OR 2 More preferably, R 1 The group is -C(O)-OR 2 ', where R 2 'Branched or cyclic C3-C 12 Alkyl groups, optionally interspersed with one or two oxygen atoms. R 2 Preferably, it is branched C6-C 10 Alkyl groups, such as 2-ethylhexyl.

[0023] R in equation (I) above 2 For straight chain C1-C 12 Alkyl, branched or cyclic C3-C 12 Alkyl, straight-chain C2-C 12 alkenyl, or branched or cyclic C3-C 12 Alkenyl group. R group 2 C1-C 12 Alkyl, branched or cyclic C3-C 12 Alkyl, straight-chain C2-C 12 alkenyl, or branched or cyclic C3-C 12 The alkenyl group may optionally be intercalated with one or more oxygen atoms, such as, for example, one or two oxygen atoms. In a preferred embodiment, R 2 Branched or cyclic C3-C 12 Alkyl groups, optionally intercalated with one or two oxygen atoms. More preferably, R 2 For branched C6-C 10 Alkyl groups, such as 2-ethylhexyl.

[0024] R in equation (I) above 4 It can be hydrogen, straight-chain C1-C8 alkyl, branched or cyclic C3-C8 alkyl, straight-chain C1-C8 alkoxy, branched or cyclic C3-C8 alkoxy, straight-chain C2-C8 alkenyl, or branched or cyclic C3-C8 alkenyl. In a preferred embodiment, R 4 It is hydrogen, a straight-chain C1-C4 alkyl group, or a branched C3-C4 alkyl group. Preferably, R 4 It is hydrogen or methyl, more preferably hydrogen.

[0025] In addition, R 3 Or R 4 One of them and R 1 Together with the carbon atoms they are attached to, they can form 5- to 18-membered saturated or unsaturated rings, which may optionally be interspersed with one or more oxygen atoms. For example, R 3 Or R 4 One of them and R 1 Together with the carbon atoms they are attached to, they can form 5- to 6-membered saturated or unsaturated rings, which may optionally be interspersed with one or two oxygen atoms. R 3 and R 4 They can also form 5- to 18-membered saturated or unsaturated rings together with the carbon atoms they are attached to, which may optionally be interspersed with one or more oxygen atoms. For example, R 3 and R 4 They can form 5- or 6-membered saturated or unsaturated rings together with the carbon atoms they are attached to, which may optionally be interspersed with one or two oxygen atoms. Furthermore, R 1 R 3 and R 4 They can form 5- to 12-membered saturated or unsaturated bicyclic rings together with the carbon atoms they are attached to, and these bicyclic rings may optionally be interspersed with one or more oxygen atoms. For example, R 1 R 3 and R 4 They can form 5- to 6-membered saturated or unsaturated bicyclic rings together with the carbon atoms they are attached to, and these bicyclic rings may optionally be interspersed with one or two oxygen atoms.

[0026] R in equation (I) 5 and R 5 'Independently hydrogen or groups -OR 6 -OR group 6 R in 6 Independently hydrogen, straight-chain C1-C8 alkyl, branched or cyclic C3-C8 alkyl, straight-chain C2-C8 alkenyl, or branched or cyclic C3-C8 alkenyl, preferably R 6 Independently, it is hydrogen, a straight-chain C1-C4 alkyl group, or a branched C3-C4 alkyl group. In a preferred embodiment, R 5 and R 5 Each of them is independently hydrogen, -O-CH3, or -OCH2CH3. Preferably, R 5 and R 5 'All are -O-CH3.'

[0027] According to the discovery of the present invention, exemplary compounds compatible with cyanoacrylates and not belonging to any hazardous category are commercially available, including, for example, those produced by Merck KGaA (Germany). ST or ST Liquids sells diethylhexyl eugenol malonate (2-(4-hydroxy-3,5-dimethoxybenzyl)-malonate bis-(2-ethylhexyl) ester; CAS No.: 444811-29-4). Another illustrative commercially available example suitable according to the invention is Merck KGaA (Germany). AP sells bis(2-ethylhexyl)2-[(4-hydroxy-3,5-dimethoxyphenyl)methyl]malonate (CAS No.: 872182-46-2). Other exemplary compounds include, but are not limited to, diethyl [(4-hydroxy-3-methoxyphenyl)methylene]malonate (CAS No.: 24331-83-7) or 2-[(3,4,5-trimethoxyphenyl)methylene]-1,3-diethyl malonate (CAS No.: 51444-50-9).

[0028] The compounds described above are not classified as hazardous and are described for use in cosmetics, for example, in WO 2019 / 229401. However, their compatibility with cyanoacrylate systems is not described in the literature at all. In contrast, the inventors have unexpectedly discovered that such compounds can be used as non-hazardous free radical stabilizers in cyanoacrylate compositions.

[0029] Based on the total weight of the curable cyanoacrylate composition, the curable cyanoacrylate composition according to the present invention may contain, for example, 0.1% to 5.0% by weight of at least one free radical stabilizer of formula (I). In a preferred embodiment, based on the total weight of the curable cyanoacrylate composition, the curable cyanoacrylate composition contains 0.2% to 4.0% by weight, more preferably 0.3% to 3.0% by weight of at least one free radical stabilizer of formula (I).

[0030] The curable cyanoacrylate composition according to the present invention also naturally comprises at least one cyanoacrylate monomer. Suitable cyanoacrylate compositions are known in the art. The present invention is not limited to a specific type of cyanoacrylate monomer. For example, the cyanoacrylate monomer may be selected from at least one of the formula R 7 HC = C(CN) - COOR 8 The compound in which R 7 Hydrogen, straight-chain or branched C1-C 15 Alkyl, straight-chain or branched C2-C 15 Alkenyl, straight-chain or branched C2-C 15 Alkyne group, straight chain or branched C2-C 15 alkoxy, cycloalkyl, aralkyl, allyl, or aryl, wherein R 7Optionally, it may be further subjected to at least one halogen and / or at least one C1-C 15 Alkoxy group substitution; and R 8 Hydrogen, straight-chain or branched C1-C 15 Alkyl, straight-chain or branched C2-C 15 Alkenyl, straight-chain or branched C2-C 15 Alkyne group, straight chain or branched C2-C 15 alkoxy, cycloalkyl, aralkyl, or aryl, wherein R 8 Optionally, it may be further subjected to at least one halogen and / or at least one C1-C 15 Alkoxy group substitution;

[0031] In a preferred embodiment, the at least one cyanoacrylate monomer is selected from methyl cyanoacrylate, ethyl cyanoacrylate, propyl cyanoacrylate, butyl cyanoacrylate, octyl cyanoacrylate, allyl cyanoacrylate, β-methoxyethyl cyanoacrylate, β-ethoxyethyl cyanoacrylate, and combinations thereof. Ethyl cyanoacrylate is particularly preferred.

[0032] The amount of cyanoacrylate monomer in the curable cyanoacrylate composition according to the present invention is not particularly limited. For example, based on the total weight of the curable cyanoacrylate composition, the curable cyanoacrylate composition may contain at least 50% by weight of at least one cyanoacrylate monomer. In a preferred embodiment, based on the total weight of the curable cyanoacrylate composition, the curable cyanoacrylate composition contains from 60.0% by weight to 99.9% by weight of at least one cyanoacrylate monomer. Preferably, based on the total weight of the curable cyanoacrylate composition, the curable cyanoacrylate composition contains from 88.0% by weight to 99.8% by weight, more preferably from 97.0% by weight to 99.5% by weight of at least one cyanoacrylate monomer.

[0033] As is known in the art, cyanoacrylates can also undergo anionic polymerization. Therefore, cyanoacrylate compositions typically also contain anionic stabilizers (also known as "acid stabilizers") to prevent anionic polymerization. Anionic stabilizers are typically selected from Lewis acids or Brønsted acids. Therefore, the curable cyanoacrylate compositions according to the invention typically also contain Lewis acids or Brønsted acids as anionic stabilizers. The anionic stabilizer is preferably selected from boron trifluoride (BF3 and its complexes), sulfur dioxide (SO2), or hydrogen fluoride (HF). Based on the total weight of the curable cyanoacrylate composition, the anionic stabilizer may be included in the curable cyanoacrylate composition, for example, in an amount from 0.0005% by weight to 5.0% by weight.

[0034] The cyanoacrylate composition may also contain other additives well known in the art. For example, the curable cyanoacrylate composition according to the invention may also include commonly used additives selected from, for example, thickeners, thixotropic agents, accelerators, retarders, plasticizers, tackifiers, pigments or dyes. Those skilled in the art will be able to readily select suitable additives and their amounts as needed. For example, based on the total weight of the curable cyanoacrylate composition, other additives typically used in cyanoacrylate compositions may be present in the curable cyanoacrylate composition according to the invention in an amount of up to 60% by weight. From a performance perspective, based on the total weight of the curable cyanoacrylate composition, such conventional additives are present in the curable cyanoacrylate composition according to the invention in an amount preferably up to only 45% by weight, more preferably up to 30% by weight.

[0035] This invention is also suitable for stabilizing photocurable cyanoacrylate compositions, such as UV-curable cyanoacrylate compositions, to prevent free radical polymerization. Photocurable cyanoacrylate compositions are known in the art and described, for example, in U.S. Patent 5,922,783 or WO 2020 / 206405. Photocurable cyanoacrylate compositions typically contain metallocene compounds and photoinitiators, as known to those skilled in the art. Therefore, in one embodiment, this invention relates to a curable cyanoacrylate composition as described above, which further contains a metallocene compound and a photoinitiator. Those skilled in the art will be able to select suitable metallocene compounds or photoinitiators and their amounts, for example, referring to U.S. Patent 5,922,783 or WO 2020 / 206405.

[0036] The curable cyanoacrylate compositions according to the invention can be used in any field where cyanoacrylate adhesives are commonly used. Examples include, but are not limited to, industrial manufacturing or domestic use. The invention, using a non-hazardous free radical stabilizer, is particularly advantageous in fields where cyanoacrylate adhesives come into contact with humans, such as in toy manufacturing, food or beverage container manufacturing, or in the cosmetics field, for example, for cosmetic packaging or articles bonded to the skin, such as for adhesive false eyelashes, and in the medical field, for example, as liquid plaster.

[0037] The present invention also relates to the use of compounds of formula (I) as defined above for inhibiting free radical polymerization in compositions comprising at least one cyanoacrylate monomer. Alternatively, the present invention relates to a method for inhibiting free radical polymerization in compositions comprising at least one cyanoacrylate monomer, the method comprising the step of adding at least one compound of formula (I) to the composition. Preferred embodiments of the use (or method) of, for example, preferred compounds of formula (I) or preferred cyanoacrylate monomers and their amounts according to the invention have been described above in embodiments relating to curable cyanoacrylate compositions of the present invention.

[0038] The invention is further illustrated by the following examples.

[0039] Example

[0040] Material :

[0041] Cyanoacrylate monomer: Ethyl cyanoacrylate

[0042] Free radical stabilizers:

[0043] Comparative examples: hydroquinone (HQ), butylated hydroxyanisole (BHA)

[0044] According to the present invention: ST (named O.ST in Table 1 below) or AP (named R.AP in Table 1), both are from Merck KGaA (Germany).

[0045] Cyanoacrylate monomer (CA) was purified directly from the production vessel by vacuum distillation. Certain quantities required for testing were re-imported into a separate vessel. Immediately after removing the vessel from the distillation line, 5 ppm of an acid stabilizer (BF3-complex) was added to prevent immediate polymerization. Purity levels were checked using GC-MS and HPLC. >99.5% of the cyanoacrylate monomer was detected in further used sample amounts, with the absence of hydroquinone (HQ).

[0046] In the second step, a portion of the pre-stabilized cyanoacrylate was removed and a free radical stabilizer was added to achieve the concentrations listed in Table 1 below. Samples containing poly(methyl methacrylate) (PMMA) as a thickener were also prepared.

[0047] Table 1: Sample Compositions [wt%]

[0048] CA HQ BHA O.ST R.AP PMMA CE1 99.0 1 CE2 99.0 1 IE1 97.5 2.5 IE2 97.5 2.5 IE3 99.0 1 IE4 99.0 1 IE5 99.5 0.5 IE6 99.5 0.5 IE7 94.5 0.5 5 IE8 94.5 0.5 5

[0049] Comparative Examples 1 (CE1) and 2 (CE2) used conventional free radical stabilizers known for use with cyanoacrylates. Examples 1 to 8 (IE1 to IE8) of the present invention used non-hazardous free radical stabilizers selected according to the present invention.

[0050] (According to the recording standards of ISO 9001 or IATF 16949) The viscosity of the sample composition was determined using a cone-plate rheometer at +20°C and 160 rpm. Table 2 below shows the average results of three measurements.

[0051] The term “14d, 60°C” in Table 2 means that the liquid adhesive sample was aged at +60°C for 14 days (before preparing the sample including the substrate further described below).

[0052] The term "360d, 22°C" indicates that the liquid adhesive sample has been aged at ambient temperature for one year.

[0053] Table 2: Average viscosity of fresh and aged sample compositions [mPa·s]

[0054] initial 14d，60℃ 360d，22℃ CE1 2 2 3 CE2 2 5 7 IE1 3 3 3 IE2 3 3 3 IE3 2 3 2 IE4 2 3 3 IE5 2 4 4 IE6 2 5 4 IE7 463 489 510 IE8 455 512 533

[0055] As can be seen from Table 2 above, the non-hazardous free radical stabilizer used according to the present invention exhibits good compatibility with cyanoacrylate monomers and effectively prevents polymerization at a level similar to that of conventional "toxic" free radical stabilizers used to date in the art. This even applies to the presence of additives commonly used in the cyanoacrylate field, such as the thickeners seen in Examples IE7 and IE8 of the present invention.

[0056] The reactivity of the sample composition was tested by bonding the surfaces of EPDM rubber profiles together using the sample composition as an adhesive. The average curing times obtained after five tests are listed in Table 3 below.

[0057] Table 3: Setting time on EPDM [s]

[0058] initial 14d，60℃ 360d，22℃ CE1 1 1 1 CE2 1 2 2 IE1 7 8 7 IE2 8 10 9 IE3 2 2 2 IE4 2 2 3 IE5 1 1 1 IE6 1 1 2 IE7 2 3 3 IE8 2 3 3

[0059] As can be seen from Table 3 above, the non-hazardous free radical stabilizer selected according to the present invention substantially does not impair the reactivity of the resulting cyanoacrylate composition. On the contrary, the reactivity is at an acceptable level within the same range as in the presence of conventional free radical stabilizers.

[0060] The mechanical strength obtained using the sample composition was tested by bonding clean steel samples without further pretreatment (following the guidelines of DIN EN 1465). The average data from three tests are shown in Table 4 below.

[0061] Table 4: Average Shear Strength Test Results of Steel Samples [N mm] -2 ]

[0062] initial 14d，60℃ CE1 22 21 CE2 18 16 IE5 21 20 IE6 21 18 IE7 20 21 IE8 19 20

[0063] The mechanical strength of the adhesive bond is not compromised due to the presence of the non-hazardous free radical stabilizer selected according to the present invention.

[0064] Surprisingly, conventional free radical stabilizers can be replaced by non-hazardous free radical stabilizers selected according to the present invention. The non-hazardous free radical stabilizers selected according to the present invention can be well formulated into cyanoacrylates. The sample compositions achieve similar properties, for example, in terms of shelf life and adhesive properties, compared to prior art compositions containing hazardous stabilizers such as HQ or BHA.

Claims

1. A curable cyanoacrylate composition comprising (i) at least one cyanoacrylate monomer, and (ii) at least one free radical stabilizer The free radical stabilizer comprises one or more compounds of formula (I). (I) Where (x) represents a double bond and R 3 It does not exist, or (x) represents a single bond and R 3 It is hydrogen; R 1 The group is -C(O)-OR 2 ', where R 2 'For linear C1-C 12 Alkyl, branched or cyclic C3-C 12 Alkyl, straight-chain C2-C 12 alkenyl, or branched or cyclic C3-C 12 alkenyl; R 2 For straight chain C1-C 12 Alkyl, branched or cyclic C3-C 12 Alkyl, straight-chain C2-C 12 alkenyl, or branched or cyclic C3-C 12 alkenyl; R 4 It is hydrogen; and R 5 and R 5 'Independently hydrogen or the group -O-CH3.

2. The curable cyanoacrylate composition according to claim 1, wherein in formula (I), R 1 The group is -C(O)-OR 2 ', where R 2 'Branched or cyclic C3-C 12 alkyl; R 2 Branched or cyclic C3-C 12 alkyl.

3. The curable cyanoacrylate composition according to claim 2, wherein in formula (I), R 1 The group is -C(O)-OR 2 ', where R 2 'For branching C6-C 10 alkyl; R 2 For branched C6-C 10 alkyl.

4. The curable cyanoacrylate composition according to claim 3, wherein in formula (I), R 5 and R 5 ' is -O-CH3.

5. The curable cyanoacrylate composition according to any one of claims 1 to 4, wherein the cyanoacrylate monomer is selected from at least one compound of the following formula: R 7 HC=C(CN)-COOR 8 ,in R 7 Hydrogen, straight-chain or branched C1-C 15 Alkyl, straight-chain or branched C2-C 15 Alkenyl, straight-chain or branched C2-C 15 Alkyne group, straight chain or branched C2-C 15 alkoxy, cycloalkyl, aralkyl, allyl, or aryl, wherein R 7 Optionally, it may be further subjected to at least one halogen and / or at least one C1-C 15 Alkoxy group substitution; and R 8 Hydrogen, straight-chain or branched C1-C 15 Alkyl, straight-chain or branched C2-C 15 Alkenyl, straight-chain or branched C2-C 15 Alkyne group, straight chain or branched C2-C 15 alkoxy, cycloalkyl, aralkyl, or aryl, wherein R 8 Optionally, it may be further subjected to at least one halogen and / or at least one C1-C 15 Alkoxy group substitution.

6. The curable cyanoacrylate composition according to claim 5, wherein the cyanoacrylate monomer is selected from methyl cyanoacrylate, ethyl cyanoacrylate, propyl cyanoacrylate, butyl cyanoacrylate, octyl cyanoacrylate, allyl cyanoacrylate, β-methoxyethyl cyanoacrylate, β-ethoxyethyl cyanoacrylate, and combinations thereof.

7. The curable cyanoacrylate composition according to any one of claims 1 to 4, 6, wherein, based on the total weight of the curable cyanoacrylate composition, the composition comprises 0.1% to 5.0% by weight of the at least one free radical stabilizer.

8. The curable cyanoacrylate composition according to claim 7, wherein, based on the total weight of the curable cyanoacrylate composition, the composition comprises from 0.2% to 4.0% by weight of the at least one free radical stabilizer.

9. The curable cyanoacrylate composition according to claim 7, wherein, based on the total weight of the curable cyanoacrylate composition, the composition comprises from 0.3% to 3.0% by weight of the at least one free radical stabilizer.

10. The curable cyanoacrylate composition according to any one of claims 1 to 4, 6, 8, and 9, wherein, based on the total weight of the curable cyanoacrylate composition, the composition comprises at least 50% by weight of the at least one cyanoacrylate monomer.

11. The curable cyanoacrylate composition of claim 10, wherein, based on the total weight of the curable cyanoacrylate composition, the composition comprises from 60.0% to 99.9% by weight of the at least one cyanoacrylate monomer.

12. The curable cyanoacrylate composition of claim 10, wherein, based on the total weight of the curable cyanoacrylate composition, the composition comprises from 88.0% to 99.8% by weight of the at least one cyanoacrylate monomer.

13. The curable cyanoacrylate composition of claim 10, wherein, based on the total weight of the curable cyanoacrylate composition, the composition comprises from 97.0% to 99.5% by weight of the at least one cyanoacrylate monomer.

14. The curable cyanoacrylate composition according to any one of claims 1 to 4, 6, 8, 9, 11 to 13, further comprising an anionic stabilizer, wherein the anionic stabilizer is a Lewis acid or a Brønsted acid.

15. The curable cyanoacrylate composition according to claim 14, wherein the anionic stabilizer is selected from boron trifluoride (BF3) and its complexes, sulfur dioxide (SO2) or hydrogen fluoride (HF).

16. The curable cyanoacrylate composition of claim 14, wherein, based on the total weight of the curable cyanoacrylate composition, the composition comprises from 0.0005% by weight to 5.0% by weight of the anionic stabilizer.

17. The curable cyanoacrylate composition of claim 15, wherein, based on the total weight of the curable cyanoacrylate composition, the composition comprises from 0.0005% by weight to 5.0% by weight of the anionic stabilizer.

18. The curable cyanoacrylate composition according to any one of claims 1 to 4, 6, 8, 9, 11 to 13, 15 to 17, further comprising additional additives selected from thickeners, thixotropic agents, accelerators, retardants, plasticizers, tackifiers, pigments or dyes.

19. The curable cyanoacrylate composition of claim 18, wherein the additional additive is present in an amount of up to 60% by weight based on the total weight of the curable cyanoacrylate composition.

20. The curable cyanoacrylate composition of claim 18, wherein the additional additive is present in an amount of up to 45% by weight based on the total weight of the curable cyanoacrylate composition.

21. The curable cyanoacrylate composition of claim 18, wherein the additional additive is present in an amount of up to 30% by weight based on the total weight of the curable cyanoacrylate composition.

22. The curable cyanoacrylate composition according to any one of claims 1 to 4, 6, 8, 9, 11 to 13, 15 to 17, 19 to 21, further comprising a metallocene compound and a photoinitiator.

23. Use of the compound of formula (I) for inhibiting free radical polymerization in compositions comprising at least one cyanoacrylate monomer. (I) Where (x) represents a double bond and R 3 It does not exist, or (x) represents a single bond and R 3 It is hydrogen; R 1 The group is -C(O)-OR 2 ', where R 2 'For linear C1-C 12 Alkyl, branched or cyclic C3-C 12 Alkyl, straight-chain C2-C 12 alkenyl, or branched or cyclic C3-C 12 alkenyl; R 2 For straight chain C1-C 12 Alkyl, branched or cyclic C3-C 12 Alkyl, straight-chain C2-C 12 alkenyl, or branched or cyclic C3-C 12 alkenyl; R 4 It is hydrogen; and R 5 and R 5 'Independently hydrogen or the group -O-CH3.

24. An article comprising the curable cyanoacrylate composition according to claim 1.

25. The article of claim 24, wherein the article is selected from the group consisting of: food containers, beverage containers, cosmetic packaging, and articles adhered to the skin.

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