CN113943535A

CN113943535A - High-filling type permeable sealant

Info

Publication number: CN113943535A
Application number: CN202111237412.3A
Authority: CN
Inventors: 郑理; 项尚林; 王博
Original assignee: Nanjing Abnen Sealing Technology Stock Co ltd
Current assignee: Nanjing Abnen Sealing Technology Stock Co ltd
Priority date: 2021-10-22
Filing date: 2021-10-22
Publication date: 2022-01-18

Abstract

The invention discloses a high-filling type permeable sealant, which relates to the technical field of acrylate sealant preparation. By using the inorganic rigid particles and the chain-like organic oligomer, the volume shrinkage rate before and after the polymerization of the penetrating sealant is obviously reduced, the filling rate of the micropore defects in the workpiece is improved, and the improvement of the qualification rate and the service life of the workpiece are facilitated.

Description

High-filling type permeable sealant

Technical Field

The invention relates to a permeable sealant which permeates into tiny pores of a workpiece based on pressure difference and performs chemical polymerization reaction to block the pores of the workpiece, in particular to a high-filling type permeable sealant consisting of a functional acrylate monomer and other additives.

Background

The traditional inorganic water glass or unsaturated polyester type infiltration sealant has higher viscosity, so the traditional inorganic water glass or unsaturated polyester type infiltration sealant is diluted by water (used for inorganic water glass type) or polar organic solvent (used for unsaturated polyester type) in the using process, and the viscosity of the traditional inorganic water glass or unsaturated polyester type infiltration sealant is reduced so as to be beneficial to the infiltration of the traditional inorganic water glass or unsaturated polyester type infiltration sealant into micropore defects; in the curing process, water or solvent needs to be removed, so that the volume of the sealant is obviously shrunk before and after curing, the filling rate of micropore defects is low, the sealing effect is poor, and the air tightness is poor.

At present, common penetrating sealant is a liquid functional acrylate monomer mixture with low viscosity, permeates into the interior of tiny defects of a metal casting by means of pressure difference generated by special equipment, and polymerization and solidification of acrylate in the interior of tiny holes are initiated by means of heating and the like, so that the purpose of blocking the defects of a workpiece is achieved.

Ideally, a cured product formed after the penetrating sealant is cured in the pore should be tightly attached to the four walls of the pore to completely block the pore, but the penetrating sealant shrinks in volume due to the addition polymerization reaction between molecules in the curing process, once the pore to be blocked is large, a glue stick formed after the penetrating sealant penetrating into the pore is cured generates a gap between the shrunk glue stick and the pore wall to form an effect of insufficient filling. The air tightness of the workpiece is reduced due to the gap, the conditions of point leakage and line leakage cannot be improved, the qualified rate of the workpiece is low, the effect of a permeation sealing process is weakened, and the requirements of industrial production cannot be completely met; the solvent is easy to enter a gap between the rubber column and the pore wall due to the capillary action, and compared with the condition that the solvent can only contact the casting wall from the end face when the solvent is completely blocked, the contact area is larger under the condition, the corrosion of the small hole in the casting is more likely to be accelerated, the service life of the casting is shortened, and the potential safety hazard is reduced.

The widely used acrylate-based penetrating sealant at present takes liquid acrylate as a main body, does not need water or solvent to adjust viscosity, generates free radical polymerization reaction in the curing process, belongs to bulk polymerization, has no solvent removal process, and reduces the volume shrinkage before and after curing. However, in the polymerization process, due to the characteristics of slow initiation, fast growth and fast termination of a free radical reaction, the molecular weight is inevitably and fast increased to form regular long-chain macromolecules, and the trend of natural reduction of chemical potential in a system tends to be closely and regularly arranged to form a tightly-packed structure, so that the intermolecular distance after polymerization is obviously reduced, the reaction macroscopically means that the volume of the sealant after curing is still greatly shrunk, and the filling rate of the sealant to micropore defects still has certain defects. The current industrial solution is to apply the impregnating sealant to the same workpiece two or three times, but this involves significant cost and work-time pressures.

Disclosure of Invention

The technical problems to be solved by the invention are as follows: the prior common permeable sealing adhesive has larger volume shrinkage rate before and after curing, and after the permeable sealing adhesive is filled into the pores of a workpiece, the permeable sealing adhesive shrinks before and after curing, so that the porosity filling rate is reduced, and the phenomena of incomplete plugging of the pores of the workpiece, reduced reliability when the workpiece is corroded by chemical corrosion and solvents, low qualified rate of the workpiece and the like occur.

In order to solve the technical problems, the invention provides the following technical scheme:

a high-filling type permeable sealant is prepared by mixing monofunctional acrylate, polyfunctional acrylate, a composite emulsifier, an initiator and a polymerization inhibitor, and comprises the following components in parts by weight:

preferably, the monofunctional acrylate is an alkyl ester of (meth) acrylic acid having 10 to 18 carbon atoms.

Preferably, the monofunctional acrylate is one or more of lauryl acrylate, lauryl methacrylate, isodecyl methacrylate, octadecyl acrylate, octadecyl methacrylate, tridecyl acrylate and tridecyl methacrylate.

Preferably, the multifunctional acrylate is one or more of (meth) acrylic acid polyethylene glycol ester, 1, 6-hexanediol diacrylate, 2-butyl-2-ethyl-1, 3-propanediol diacrylate, 2-methyl-1, 3-propanediol diacrylate and 1, 4-butanediol diacrylate.

Preferably, the compound emulsifier is one or more of polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan monolaurate, polyethylene glycol mono-octyl phenyl ether and castor oil polyoxyethylene ether.

Preferably, the inorganic rigid particles are one or more of nano silica, nano calcium carbonate, nano magnesium oxide and commercial derivatives thereof subjected to surface treatment by using a coupling agent.

Preferably, the chain organic oligomer is one or more of polyethylene glycol (200) dimethacrylate, polyethylene glycol (400) dimethacrylate and polyethylene glycol (600) dimethacrylate.

Preferably, the initiator is one of azobisisobutyronitrile and azobisisoheptonitrile.

Preferably, the polymerization inhibitor is one or more of hydroquinone, benzoquinone, naphthoquinone, anthraquinone, 2, 6-dibutyl p-cresol, picric acid, 4-methoxyphenol, naphthoquinone, phenothiazine, 2, 6-di-tert-butylphenol, 2, 5-di-tert-butylhydroquinone, 2, 5-di-tert-butyl-1, 4-benzoquinone and 2, 6-di-tert-butyl-4-ethyl benzoquinone.

The invention has the following beneficial effects:

the invention provides a high-filling-rate permeation sealant which takes low-viscosity acrylate monomers as main components and takes inorganic rigid particles and chain organic oligomers as auxiliary filling components. Under the condition that basic performances such as cleaning performance, stability and the like are not changed, the volume shrinkage rate before and after curing is greatly reduced, the internal pore filling rate of the workpiece is improved, the requirement of efficiently filling the pores of the workpiece is met, the reliability of resisting chemical corrosion and solvent corrosion is improved, and the service life of the workpiece is prolonged.

Detailed Description

The following examples are included to provide further detailed description of the present invention and to provide those skilled in the art with a more complete, concise, and exact understanding of the principles and spirit of the invention.

Example 1: the invention is composed of monofunctional acrylate, polyfunctional acrylate, composite emulsifier, initiator and polymerization inhibitor, and the components by weight portion are as follows:

and (3) adding the raw materials into a stirring kettle according to the proportion, and mixing for 30-60min to obtain the high-filling type permeable sealant.

The above-mentioned monofunctional acrylate is C10-18 alkyl ester of (meth) acrylic acid, such as one or more of lauryl acrylate, lauryl methacrylate, isodecyl methacrylate, stearyl acrylate, stearyl methacrylate, tridecyl acrylate, and tridecyl methacrylate.

The multifunctional acrylate is one or more of (methyl) acrylic acid polyethylene glycol ester, 1,6 hexanediol diacrylate, 2-butyl-2-ethyl-1, 3-propylene glycol diacrylate, 2-methyl-1, 3-propylene glycol diacrylate and 1, 4-butanediol diacrylate.

The composite emulsifier is one or more of polyoxyethylene sorbitan monooleate (TW-80), polyoxyethylene sorbitan monolaurate (TW-20), polyethylene glycol mono-octyl phenyl ether (OP-10) and castor oil polyoxyethylene ether (EL-40).

The inorganic rigid particles are one or more of nano silicon dioxide, nano calcium carbonate, nano magnesium oxide and commercial derivatives thereof subjected to surface treatment by using a coupling agent.

The chain organic oligomer is one or more of polyethylene glycol (200) dimethacrylate, polyethylene glycol (400) dimethacrylate and polyethylene glycol (600) dimethacrylate.

The initiator is one of azobisisobutyronitrile and azobisisoheptonitrile.

The polymerization inhibitor is one or more of hydroquinone, benzoquinone, naphthoquinone, anthraquinone, 2, 6-dibutyl p-cresol, picric acid, 4-methoxyphenol, naphthoquinone, phenothiazine, 2, 6-di-tert-butylphenol, 2, 5-di-tert-butylhydroquinone, 2, 5-di-tert-butyl-1, 4-benzoquinone and 2, 6-di-tert-butyl-4-ethyl benzoquinone.

According to the invention, inorganic rigid particles are compounded with chain organic oligomers, and an optimized acrylate monomer is added, so that the volume shrinkage rate before and after curing of the permeable sealant is reduced under the combined action, and the filling rate of pores is improved.

TABLE 1 comparison of volume shrinkage for typical sealant types

Kind of sealant	Inorganic water glass	Unsaturated polyester	Acrylate radical	The invention
					Volume shrinkage/%	≥60	40-60	15-30	3-8

For inorganic rigid particles, the inorganic rigid particles do not react in the polymerization process, act as inert fillers, and reduce the shrinkage after polymerization due to the existence of the inorganic rigid particles. And because the inorganic matter has limited compatibility in organic matters, inorganic rigid particles independently exist in the polymer after polymerization, the rigid particles are used as cores, and the chain-shaped high molecules coated outside are used as interface layers to form a 'sea-island' structure, so that the close accumulation of the original regular long-chain high molecules is further destroyed, the drawing of the distance between the molecules is reduced, and the volume shrinkage rate before and after curing is macroscopically reduced.

As for the chain organic oligomer, the molecular weight of the chain organic oligomer is about 200-600, and the chain organic oligomer is arranged in an acrylate molecular chain in a block form in the polymerization process, so that the regularity of the molecular chain is damaged, the close packing of regular long-chain macromolecules is reduced, and the free volume of the molecule of the internal chain segment is basically unchanged, so that the chain organic oligomer plays a skeleton role in a polymer network after polymerization, the excessive approach among the molecular chains is avoided, and the volume shrinkage is further reduced.

The main difficulty of adding the inorganic rigid particles is that the compatibility of inorganic matters in an organic system is limited, and the acrylate-based permeable sealant has low viscosity and is easy to settle in the storage process after being added in a large amount, so that the stability of the whole system is influenced. Some previous studies (Chinese trumpet et al, China Adhesives 2012, 21 (1): 15-19) showed that when the amount of inorganic rigid particles added exceeds 3%, the sealant system is prone to sedimentation and turbidity. To solve this problem, three improvements are required:

1. after the inorganic rigid particles are added, the stirring and dispersing process is enhanced, the inorganic rigid particles are uniformly dispersed as much as possible, and the possibility of agglomeration and sedimentation is reduced;

2. surface modification of inorganic rigid particles, or selection of commercial derivatives with appropriate surface modification;

3. the use amount of the emulsifier is properly increased, and a plurality of emulsifiers are reused, so that the dispersion stability of the system is ensured.

For the process aspect of enhancing stirring and dispersion, the conventional osmotic sealing gum usually adopts a common stirrer and a planetary stirrer in the manufacturing process, has good effect on dispersing low-viscosity liquid, but is not suitable for dispersing inorganic rigid particles. The solution is to use a high-speed centrifugal disperser instead. Taking the observation effect of adding 10 parts of nano silicon dioxide into 100 parts of acrylate monomer without surfactant and standing for 7 days as an example:

TABLE 2 influence of centrifugal rotational speed on dispersion and sedimentation of inorganic rigid particles

After the high-speed centrifugal dispersion process is used, the distribution uniformity and stability of the inorganic rigid particles in the sealant are greatly improved. The inorganic rigid particles in a mass fraction of 10% may also be uniformly distributed in the acrylate monomer and remain stable for a period of time. Wherein, the influence of increasing the centrifugal rotating speed is more obvious, and the process time is prolonged to a certain extent, but the sedimentation problem can not be thoroughly solved.

The higher the amount of the inorganic rigid particles added, the higher the tendency of the inorganic rigid particles to spontaneously aggregate in the organic phase due to incompatibility between the organic and inorganic substances. The surface modification of the inorganic rigid particles can graft/compound an organic functional group layer on the surface layer of the inorganic rigid particles, increase the compatibility of the inorganic rigid particles in an organic phase and improve the distribution condition. Typically, silane coupling agent KH550 is added into nano silicon dioxide in a mass fraction of 3-5%, dispersed and mixed for 2h at 60 ℃ by a solid stirrer, treated nano silicon dioxide powder is added into 100 parts by weight of acrylate monomer without surfactant in a weight ratio of 10 parts, and the dispersion process is high-speed centrifugal dispersion, 2000r/min and 30min, so that the effect of no sedimentation within 7 days can be achieved, and the dispersion stability is obviously improved. Some surface-modified rigid particles with surface functional groups that are more compatible with selected acrylate monomers, such as fumed nanosilica HB-132 modified with hexamethyldisilazane, have comparable or better results.

The principle of increasing the dosage of the emulsifier and reusing various emulsifiers is that the emulsifier molecules are amphiphilic molecules with one polar end and one non-polar end, and can be compatible with the outer functional group layer of the inorganic rigid particles with modified surfaces, the particles are wrapped to form micelles, and the micelles are suspended in a liquid phase to keep stable and maintain the stable time of dispersion. 10 parts by weight of mixed emulsifier OP-10 and EL-40 (mixed according to the mass ratio of 1: 1) are used, acrylic monomers without surfactant are added, 10 parts of KH550 modified nano silicon dioxide are mixed, the mixture is dispersed for 30min at 2000r/min on a high-speed centrifugal dispersing machine, and the final finished product is placed for more than 45 days without any sedimentation phenomenon.

The key point of adding the chain organic oligomer is that the oligomer forms a block in a polymer network after polymerization, the regularity of a chain is damaged, a structure similar to a fragile chain is manufactured, and the mechanical strength and the aging resistance of a final product are reduced to a certain extent while the volume shrinkage is reduced. In the prior art, the oligomer added with the polymer cannot completely participate in polymerization, cannot be rearranged and polymerized into a final polymer network structure, and plays a role of a simple plasticizer, so that the mechanical strength and the aging resistance of a final product are obviously reduced; when the epoxy resin is used for sealing glue, oligomer is separated out from the surface after curing, and the phenomenon of oil production is caused, so that the sealing effect is seriously influenced. The problems can be solved to a certain extent by using the oligomer terminated by the polymerizable functional group, because the functional groups linked at two ends of the molecular chain of the oligomer can be synchronously added into the polymerization process in the form of addition polymerization-free radical chain transfer in the polymerization process to form a block copolymer which is combined with a polymer network into a whole, the original oligomer occupies a free volume, the chain regularity is damaged, meanwhile, the influences on the mechanical strength, the chemical corrosion resistance and the like of a final product are small, and the phenomenon of oil production separated out from the oligomer is completely avoided. By controlling the molecular chain average molecular weight of the oligomer and using oligomers with various molecular weights, the mechanical strength and the tolerance of the product are not obviously influenced while the product maintains smaller volume shrinkage.

Taking the example of adding corresponding parts of polyethylene glycol 400(PEG400) and polyethylene glycol 400 dimethacrylate (DPEG400) terminated by a reaction functional group into 100 parts of acrylate monomer, taking the strength of a polymer crosslinking system after the hardness part of a cured product reacts and is cured, indirectly reflecting the mechanical strength and the aging resistance:

TABLE 3 influence of addition of chain organic oligomer on hardness of cured product

It is observed that the hardness of the cured product decreases with increasing amount of the oligomer, but the magnitude of the decrease gradually decreases with increasing amount, which is related to the fact that the state of the polymer as a whole gradually approaches the state of the oligomer with increasing amount of the oligomer. Under the same mass fraction, the DPEG400 mixed samples are higher in hardness than PEG400 samples, and the difference is more obvious along with the increase of the dosage, so that the end-capping modification of the reaction functional group is proved to be capable of enabling oligomer molecules to enter a polymer network in a block form through addition polymerization, and the excessive reduction of hardness and the like is avoided. The decrease in hardness can also be offset by the reinforcing effect of the inorganic rigid particles.

Comparison of finished products

The product is prepared by the following formula, and is dispersed by a high-speed centrifugal dispersion machine at 3000r/min for 30 min:

TABLE 4 proportion of the final product components

The main parameters of the product are compared with those of the American college product, the Japanese college product and the domestic product as follows.

The experimental mode of the first sizing qualification rate is as follows: powder metallurgy annular test pieces specified in the American navy Standard MIL-I-17563c with the volume porosity of 15-25%, wherein each group is subjected to primary sizing by a general infiltration sizing process, and the process comprises the following steps: vacuum-pumping to-0.098 MPa, and maintaining vacuum degree for 10 min; immersing the test piece into the sealant, and keeping the vacuum degree for 10 min; pressurizing to 0.4MPa, and keeping the pressure for 10 min; taking out the piece, and curing for 15min in hot water bath at 90 ℃. 50 test pieces were prepared for each group, and the number of the test pieces was judged to be acceptable by performing water examination under an air pressure of 0.33MPa, and the results are shown in Table 5.

TABLE 5 comparison of Primary sizing yields for different sealant samples

	Samples commercially available in the United states	Japanese commercial sample	Domestic sample	Finished product
					Volume shrinkage/%	26.9	21.4	22.3	4.86
Hardness of cured product	75	62	88	96
					Percent of pass of primary sizing	84	80	82	100

The results in table 5 show that the volume shrinkage of the finished product is obviously superior to that of the product in the same row, the filling rate of the finished product to the internal micropore defect of the metal workpiece is higher, and the reaction macroscopically, namely, the first sizing qualification rate is obviously superior to that of the sample in the same row. And simultaneously, the hardness of a cured product is excellent, and the mechanical property and the aging resistance of the cured product are compared with those of a similar product without defects. The finished product is stable in the service cycle of the product, and has no phenomena of sedimentation and turbidity.

In conclusion, the key point of the invention is that inorganic rigid particles are compounded with chain organic oligomers, the volume shrinkage rate before and after the curing of the permeable sealant is reduced under the combined action, and the filling rate of pores is improved. The principle of improving the filling rate of the inorganic rigid particles is that the inorganic rigid particles replace part of organic matters, and the volume shrinkage rate of the system is reduced inevitably due to the fact that the part of the inorganic rigid particles cannot shrink; because the compatibility of the inorganic substance and the organic substance is limited, an interface layer is formed at the interface between the inorganic rigid particles and the two phases of the polymer after the polymer system is solidified, and a certain space is occupied, so that the reduction of the volume shrinkage rate of the composite system is facilitated; the principle of reducing the shrinkage rate of the chain organic oligomer is that the chain organic oligomer is a long-chain molecular structure with a certain polymerization degree, the free volume of molecules does not change greatly before and after polymerization, meanwhile, the chain organic oligomer plays a role of a skeleton structure in a polymer, occupies a certain space between molecular chains, destroys a close packing mode of the molecular chains, increases the space between the molecular chains, and plays a role in reducing the volume shrinkage rate.

The above embodiments are only for illustrating the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby, and any modification made on the basis of the technical scheme according to the technical idea proposed by the present invention falls within the protection scope of the present invention; the technology not related to the invention can be realized by the prior art.

Claims

1. The high-filling type permeable sealant is characterized by being prepared by mixing monofunctional acrylate, polyfunctional acrylate, a composite emulsifier, an initiator and a polymerization inhibitor, and comprising the following components in parts by weight:

2. a highly filled osmotic sealant according to claim 1, wherein: the monofunctional acrylate is an alkyl ester of (meth) acrylic acid having 10 to 18 carbon atoms.

3. A highly filled osmotic sealant according to claim 2, wherein: the monofunctional acrylate is one or more of lauryl acrylate, lauryl methacrylate, isodecyl methacrylate, octadecyl acrylate, octadecyl methacrylate, tridecyl acrylate and tridecyl methacrylate.

4. A highly filled osmotic sealant according to claim 1, wherein: the multifunctional acrylate is one or more of (methyl) acrylic acid polyethylene glycol ester, 1, 6-hexanediol diacrylate, 2-butyl-2-ethyl-1, 3-propylene glycol diacrylate, 2-methyl-1, 3-propylene glycol diacrylate and 1, 4-butanediol diacrylate.

5. A highly filled osmotic sealant according to claim 1, wherein: the composite emulsifier is one or more of polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan monolaurate, polyethylene glycol mono-octyl phenyl ether and castor oil polyoxyethylene ether.

6. A highly filled osmotic sealant according to claim 1, wherein: the inorganic rigid particles are one or more of nano silicon dioxide, nano calcium carbonate, nano magnesium oxide and commercial derivatives thereof subjected to surface treatment by using a coupling agent.

7. A highly filled osmotic sealant according to claim 1, wherein: the chain organic oligomer is one or more of polyethylene glycol (200) dimethacrylate, polyethylene glycol (400) dimethacrylate and polyethylene glycol (600) dimethacrylate.

8. A highly filled osmotic sealant according to claim 1, wherein: the initiator is one of azobisisobutyronitrile and azobisisoheptonitrile.

9. A highly filled osmotic sealant according to claim 1, wherein: the polymerization inhibitor is one or more of hydroquinone, benzoquinone, naphthoquinone, anthraquinone, 2, 6-dibutyl p-cresol, picric acid, 4-methoxyphenol, naphthoquinone, phenothiazine, 2, 6-di-tert-butylphenol, 2, 5-di-tert-butylhydroquinone, 2, 5-di-tert-butyl-1, 4-benzoquinone and 2, 6-di-tert-butyl-4-ethyl benzoquinone.