CN112646527A

CN112646527A - Low-modulus sealant and preparation method and application thereof

Info

Publication number: CN112646527A
Application number: CN202011489193.3A
Authority: CN
Inventors: 马同剑; 罗莹莹; 邢毓波; 王帅超
Original assignee: Da Yu Wei Ye Beijing International Technology Co ltd
Current assignee: Da Yu Wei Ye Beijing International Technology Co ltd
Priority date: 2020-12-16
Filing date: 2020-12-16
Publication date: 2021-04-13

Abstract

The invention provides a low-modulus sealant and a preparation method and application thereof. The sealant comprises the following raw materials: silane modified polyether resin, a water absorbent, a plasticizer, a filler, a catalyst and an auxiliary agent. The silane modified polyether resin is selected as the main component of the adhesive, the effective adhesion of the sealant and the concrete base material can be realized based on the silane group in the resin, and the sealant is a low-modulus sealant, so that the cured sealant has higher bonding strength and higher elongation at break, and the debonding problem caused by the displacement generated by the vibration of a concrete block can be effectively avoided. Meanwhile, the sealant prepared based on the raw materials has the advantages of ultraviolet resistance, aging resistance, small hardness and the like, so that the low-modulus sealant disclosed by the invention has a wide application prospect.

Description

Low-modulus sealant and preparation method and application thereof

Technical Field

The invention relates to the technical field of materials, in particular to a low-modulus sealant and a preparation method and application thereof.

Background

Along with the rapid development of domestic and foreign building material technology, the service life of building materials is longer and longer, the types of building materials are more and more abundant, the bonding requirements of expansion joints among a plurality of building materials are more and more rigorous, and various problems occur in practical application due to low bonding strength, easy aging, easy fatigue debonding, poor weather resistance and the like of conventional sealants. Moreover, the sealing materials in the prior art have single adhesive property, for example, one sealing glue generally has high adhesive strength for a certain substrate, while the other sealing glue has relatively weak adhesive strength, so that the sealing glue in the prior art has a relatively narrow application range.

Therefore, a sealant with high bonding strength, aging resistance and excellent weather resistance is needed in the technical field.

Disclosure of Invention

In order to solve the problems, the invention provides a low-modulus sealant and a preparation method and application thereof.

In a first aspect, the present invention provides a low modulus sealant, which comprises the following raw materials: silane modified polyether resin, a water absorbent, a plasticizer, a filler, a catalyst and an auxiliary agent.

Optionally, in the low-modulus sealant, the silane modified polyether resin is 10 to 50 parts by weight, the water absorbent is 0.5 to 4 parts by weight, the plasticizer is 5 to 60 parts by weight, the filler is 20 to 70 parts by weight, the catalyst is 0.1 to 1 part by weight, and the auxiliary agent is 0.8 to 25 parts by weight.

Optionally, the water absorbent is a powdered salt having a function of absorbing moisture, comprising: at least one of quick lime, soda lime, calcium chloride, magnesium chloride and phosphorus pentoxide.

Optionally, the plasticizer comprises dioctyl phthalate and/or diisononyl phthalate.

Optionally, the filler comprises: basic fillers and/or neutral fillers;

the alkaline filler comprises at least one of ground calcium carbonate, talcum powder, barium sulfate and silica powder.

Alternatively, the catalyst comprises dibutyltin dilaurate.

Optionally, the adjuvant comprises: chain extenders, thixotropic agents, pigments, auxiliary crosslinking agents and light stabilizers;

0.8-25 parts by weight of the auxiliary agent, 0-10 parts by weight of the chain extender, 0-5 parts by weight of the thixotropic agent, 0.5-15 parts by weight of the pigment, 0.2-2 parts by weight of the auxiliary crosslinking agent and 0.1-3 parts by weight of the light stabilizer.

Optionally, the chain extender comprises: at least one of dimethyl silicon glycol, dipropylene silicon glycol, polyether glycol, castor oil diol and dimethyl dimethoxy silane;

the thixotropic agent comprises oleophilic aerosil and/or polyamide wax;

the pigment comprises at least one of oleophilic titanium dioxide, carbon black and pearlescent pigment;

the auxiliary crosslinking agent is a silane coupling agent and comprises at least one of a vinyl silane coupling agent, an aminosilane coupling agent and a dimethoxysilane coupling agent;

the light stabilizer is a hindered amine light stabilizer.

In a second aspect, the present application provides a method of making a low modulus sealant as described in the first aspect above, the method comprising:

sequentially adding a plasticizer and a filler into a reaction kettle, stirring at a low speed for 5-10 minutes, heating, and stirring in vacuum to obtain a first system;

cooling the first system to room temperature, adding silane modified polyether resin, a catalyst, a water absorbent and an auxiliary agent, stirring for 30 minutes in vacuum, and discharging glue to obtain the low-modulus sealant;

wherein the heating temperature is 105-110 ℃; the vacuum stirring time is 1.5-3 hours.

In a third aspect, the present application provides a use of the low modulus sealant of the first aspect, the use comprising:

applying the low modulus sealant prepared in the first aspect to a bonded reinforced concrete substrate; or

Applying the low modulus sealant prepared in the first aspect to a bonded metal substrate; or

The low modulus sealant prepared in the first aspect is applied to the bonding of wood substrates.

In the low-modulus sealant and the preparation method and application thereof provided by the embodiment of the invention, the sealant comprises the following raw materials: silane modified polyether resin, a water absorbent, a plasticizer, a filler, a catalyst and an auxiliary agent. The silane modified polyether resin is selected as the main component of the adhesive, the effective adhesion of the sealant and the concrete base material can be realized based on the silane group in the resin, and the sealant is a low-modulus sealant, so that the cured sealant has higher bonding strength and higher elongation at break, and the debonding problem caused by the displacement generated by the vibration of a concrete block can be effectively avoided. Meanwhile, the sealant prepared based on the raw materials has the advantages of ultraviolet resistance, aging resistance, small hardness and the like, so that the low-modulus sealant disclosed by the invention has a wide application prospect.

In addition, compared with the prior art, the low-modulus sealant provided by the embodiment of the invention further has the following advantages:

1. in the low-modulus sealant provided by the embodiment of the invention, the silane modified polyether resin with a linear chain structure, which is cheap, easy to prepare, relatively environment-friendly compared with high-molecular-weight resin and has the number average molecular weight of 6000-16000 g/mol, is selected under the action of the chain extender, so that the molecular weight of the silane modified polyether resin can be increased, and the purposes of reducing the modulus of the sealant, reducing the economic cost and realizing environmental protection are achieved.

2. The low-modulus sealant provided by the embodiment of the invention is a water vapor curing sealant (namely, water in the air has a chemical reaction on the sealant to promote the curing of the sealant), and water in the environment can be absorbed into the sealant through the water absorbent so as to realize the rapid curing of the sealant.

3. The low-modulus sealant provided by the embodiment of the invention not only has excellent bonding performance on a concrete substrate, but also has excellent bonding performance on a metal substrate, and meanwhile, has excellent bonding performance on a wood substrate. Therefore, the sealant provided by the embodiment of the invention has a wide application prospect.

Drawings

FIG. 1 shows a flow chart of a method of making a low modulus sealant in an embodiment of the present invention.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below. The following examples are given for the detailed implementation and specific operation of the present invention, but the scope of the present invention is not limited to the following examples.

In a first aspect, an embodiment of the present invention provides a low modulus sealant, where the low modulus sealant comprises the following raw materials: silane modified polyether resin, a water absorbent, a plasticizer, a filler, a catalyst and an auxiliary agent. Wherein, the auxiliary agent comprises: chain extender, thixotropic agent, pigment, auxiliary crosslinking agent and light stabilizer.

In the low-modulus sealant, the weight parts of the silane modified polyether resin are 10-50, the weight parts of the water absorbent are 0.5-4, the weight parts of the plasticizer are 5-60, the weight parts of the filler are 20-70, the weight parts of the catalyst are 0.1-1, and the weight parts of the auxiliary agent are 0.8-25. Wherein, in the 0.8-25 parts by weight of the auxiliary agent, the weight parts of the chain extender is 0-10, the weight parts of the thixotropic agent is 0-5, the weight parts of the pigment is 0.5-15, the weight parts of the auxiliary crosslinking agent is 0.2-2, and the weight parts of the light stabilizer is 0.1-3.

The resin in this embodiment is silane-modified, and in the process of forming the low modulus sealant of the present invention, the silane functional groups need to chemically react with water to form silanol functional groups, and then the silanol functional groups are subjected to dehydration condensation to form a network structure of siloxane bonds, i.e., the structure of the low modulus sealant. Thus, in this example, it is desirable to add a water absorbent for absorbing water in the air to provide a source of water for the formation of silanol functional groups. In specific implementation, the water absorbent may be a powdery salt having a function of absorbing moisture, for example, at least one of quicklime, soda lime, calcium chloride, magnesium chloride, phosphorus pentoxide, and the like.

Wherein, because a certain amount of water is generated when the silanol functional groups are subjected to dehydration condensation reaction, when the silane modified polyether resin is 10 to 50 parts by weight in the specific implementation, the water absorbent is 0.5 to 4 parts by weight when the reasonable utilization of resources is considered.

On the other hand, the action of the water absorbing agent in the embodiment of the present invention further includes: the water possibly existing in the sealant is absorbed, and the storage time (shelf life) of the sealant is prolonged; during construction, the speed of the water molecules in the free sealant is reduced, so that the curing time of the sealant can be prolonged, and the construction time is prolonged.

It should be noted that the water absorbent provided by the embodiment of the present invention is an inorganic substance, and has the advantages of low toxicity, easy preparation, abundant resources, economy, low price, etc. compared with organic substances; in addition, the source of the material can be industrial waste, so that the recycling of resources can be realized.

In this example, the plasticizer functions include: promoting the movement of the molecular chain segment of the silane modified polyether resin and reducing the hardness of the sealant matrix; the solubility of the silane modified polyether resin and each auxiliary agent is promoted, so that the materials are better mixed. In particular embodiments, the plasticizer may optionally include dioctyl phthalate and/or diisononyl phthalate.

In this embodiment, the filler functions include: increasing the viscosity of the sealant; the reinforcing effect is achieved, and the tear resistance strength of the sealant is improved; the manufacturing cost of the sealant is reduced. In particular implementation, the filler may optionally include: basic fillers and/or neutral fillers. Wherein, the alkaline filler can comprise at least one of ground calcium carbonate, talcum powder, barium sulfate, silicon micropowder and the like.

In this example, the role of the catalyst includes: the activity of the silane in the silane modified polyether resin is enhanced, the combination of the silane modified polyether resin molecules and moisture is promoted, and a crosslinking reaction (namely, the dehydration condensation reaction is carried out to form a network structure of a silicon-oxygen bond) is carried out, so that the surface drying time of the low-modulus sealant is shortened. In particular embodiments, the catalyst may optionally include dibutyltin dilaurate.

In this embodiment, the chain extender functions include: the molecular weight of the silane modified polyether resin is increased, and the crosslinking density of the sealant is reduced, so that the modulus of the sealant is reduced. In specific implementation, optionally, the chain extender may include: at least one of dimethyl silicon glycol, dipropylene silicon glycol, polyether glycol, castor oil diol, dimethyl dimethoxy silane and the like.

In this embodiment, the thixotropic agent functions to include: the anti-sagging performance of the sealant is improved, so that the sealant can be well adhered to a base surface, and the adhesive capacity of the sealant is improved. In particular embodiments, the thixotropic agent may optionally include oleophilic fumed silica and/or a polyamide wax.

In this example, the role of the pigment includes: the color of the sealant is changed, the external photochromic color of the sealant is increased, and the like, so that the chromaticity of the sealant is close to the base surface, and the attractive effect is achieved. In particular embodiments, the pigment may optionally include at least one of oleophilic titanium dioxide, carbon black, and pearlescent pigments.

In this embodiment, the function of the auxiliary crosslinking agent includes: the water molecules in the air are accelerated to enter the sealant matrix, and the crosslinking reaction in the silane modified polyether resin matrix is promoted, so that the deep curing of the sealant is promoted. In specific implementation, the auxiliary crosslinking agent is optionally a silane coupling agent, and may include at least one of a vinyl silane coupling agent, an aminosilane coupling agent and a dimethoxysilane coupling agent.

In this example, the action of the light stabilizer includes: the aging resistance and the ultraviolet resistance of the sealant are improved. In particular embodiments, the light stabilizer may optionally be a hindered amine light stabilizer.

It should be noted that the above raw materials may be purchased from the market or may be prepared by the home.

In a second aspect, the present application provides a method of preparing a low modulus sealant as described in the first aspect above, as shown in fig. 1, the method comprising:

s11, sequentially adding a plasticizer and a filler into the reaction kettle, stirring at a low speed for 5-10 minutes, heating, and stirring in vacuum to obtain a first system;

s12, cooling the first system to room temperature, adding silane modified polyether resin, a catalyst, a water absorbent and an auxiliary agent, stirring for 30 minutes in vacuum, and discharging glue to obtain the low-modulus sealant;

wherein the heating temperature is 105-110 ℃; the time of vacuum stirring is 1.5 to 3 hours.

In the preparation method provided by the embodiment of the invention, the plasticizer and the filler are only required to be fully mixed at a high temperature, and then other raw materials are added at room temperature and stirred and mixed to obtain the low-modulus sealant. Therefore, the low-modulus sealant disclosed by the invention has the advantages of simple and easy preparation method, mild and easily-controlled reaction conditions, high gelling speed (gelling can be realized within 30min, the time spent in the whole preparation process is short, and the longest time is not more than 4h), and the like, so that the low-modulus sealant is easy for industrial production.

In order to provide a better understanding of the present invention to those skilled in the art, the process for preparing the low modulus sealants of the present invention is illustrated by the following examples 1-8. Moreover, unless otherwise indicated, the practice, methods and apparatus of the present invention are generally applicable to the use of reagents, methods and apparatus of the type well known in the art.

Example 1 (as a comparative example, without adding a water absorbing agent and a chain extender)

Adding 20 parts of dioctyl phthalate and 50 parts of heavy calcium carbonate into a reaction kettle in sequence, stirring at a low speed for 6 minutes, heating to 105 ℃, stirring in vacuum for 1.5 hours, cooling to room temperature, adding 40 parts of silane modified polyether resin, 0.2 part of dibutyltin dilaurate, 1 part of vinyl silane coupling agent, 0.5 part of aminosilane coupling agent, 0.1 part of hindered amine light stabilizer, 4.9 parts of lipophilic titanium dioxide, 0.1 part of carbon black and 5 parts of polyamide wax, stirring in vacuum for 30 minutes, and discharging to obtain the low-modulus sealant No. 1.

Example 2

The specific operations, reaction conditions, added raw materials and parts by weight of the present example are similar to those of example 1, except that: in the embodiment, 0.5 part of quicklime and 2 parts of dimethyl silicon glycol are added to obtain the low-modulus sealant No. 2.

Example 3

The specific operation, reaction conditions, added raw materials and parts by weight of the example are similar to those of example 2, except that: heating to 110 ℃, and stirring in vacuum for 2 hours to finally obtain the low-modulus sealant No. 3.

Example 4

The specific operation, reaction conditions, added raw materials and parts by weight of the example are similar to those of example 2, except that: heating to 110 ℃, and stirring in vacuum for 3 hours to finally obtain the low-modulus sealant No. 4.

Example 5

The specific operation and reaction conditions of this example are similar to those of example 2, except that the raw materials and components of the raw materials are different, specifically: 40 parts of silane-terminated polyether resin, 1.3 parts of vinyl silane coupling agent serving as an auxiliary crosslinking agent, 1 part of soda lime serving as a water absorbent, 20 parts of diisononyl phthalate serving as a plasticizer, 5 parts of lipophilic gas silicon serving as a thixotropic agent, 0.2 part of dibutyltin dilaurate serving as a catalyst, 0.5 part of aminosilane coupling agent and 1 part of dimethoxysilane coupling agent serving as an auxiliary crosslinking agent, 5 parts of castor oil diol serving as a chain extender, 40 parts of heavy calcium carbonate serving as a filler, 4.9 parts of titanium dioxide and 0.1 part of carbon black serving as a pigment, and finally obtaining the low-modulus sealant No. 5.

Example 6

The specific operation and reaction conditions of this example are similar to those of example 2, except that the raw materials and components of the raw materials are different, specifically: 20 parts of silane-terminated polyether resin, 1 part of dimethoxysilane coupling agent serving as an auxiliary crosslinking agent, 1 part of calcium chloride serving as a water absorbent, 20 parts of diisononyl phthalate serving as a plasticizer, 5 parts of polyamide wax serving as a thixotropic agent, 0.2 part of dibutyltin dilaurate serving as a catalyst, 0.5 part of aminosilane coupling agent serving as an auxiliary crosslinking agent, 5 parts of polyether glycol serving as a chain extender, 60 parts of heavy calcium carbonate serving as a filler, 4.9 parts of titanium dioxide and 0.1 part of carbon black serving as a pigment, and finally obtaining the low-modulus sealant No. 6.

Example 7

The specific operation and reaction conditions of this example are similar to those of example 2, except that the raw materials and components of the raw materials are different, specifically: 15 parts of silane-terminated polyether resin, 1 part of dimethoxysilane coupling agent serving as an auxiliary crosslinking agent, 3 parts of calcium chloride serving as a water absorbent, 45 parts of diisononyl phthalate serving as a plasticizer, 5 parts of polyamide wax serving as a thixotropic agent, 0.6 part of dibutyltin dilaurate serving as a catalyst, 0.5 part of aminosilane coupling agent serving as an auxiliary crosslinking agent, 5 parts of polyether glycol serving as a chain extender, 60 parts of heavy calcium carbonate serving as a filler, 4.9 parts of titanium dioxide and 0.1 part of carbon black serving as a pigment, and finally obtaining the low-modulus sealant No. 7.

Example 8

The specific operation and reaction conditions of this example are similar to those of example 2, except that the raw materials and components of the raw materials are different, specifically: 10 parts of silane-terminated polyether resin, 1 part of dimethoxysilane coupling agent serving as an auxiliary crosslinking agent, 4 parts of calcium chloride serving as a water absorbent, 40 parts of diisononyl phthalate serving as a plasticizer, 5 parts of polyamide wax serving as a thixotropic agent, 0.2 part of dibutyltin dilaurate serving as a catalyst, 0.5 part of aminosilane coupling agent serving as an auxiliary crosslinking agent, 5 parts of polyether glycol serving as a chain extender, 60 parts of heavy calcium carbonate serving as a filler, 4.9 parts of titanium dioxide and 0.1 part of carbon black serving as a pigment, and finally obtaining the low-modulus sealant No. 8.

The following table 1 shows the performance test results of the low modulus sealants prepared in the examples.

TABLE 1 test results for each of the low modulus sealants prepared above

Examples

1

2

3

4

5

6

7

8

Hardness of

38

23

25

18

20

Time to surface dry

1h

1.5h

2h

1h

Actual drying time

12h

Bonding condition

No fracture

Bonding condition: the expansion joint bonded by the sealant is broken when the expansion joint is extended to 1.5 times of the original expansion joint.

In Table 1 above, the tack-free times for examples 6-8 are relatively short because: examples 6-8 added less resin and thus increased the proportion of catalyst relatively, so the open time for examples 6-8 was shorter than the open time for examples 2-4. In example 1, the tack-free time was relatively short because: in example 1, no water-absorbing agent was added, but the water-absorbing agent initially contacted water in the air and reacted with water earlier than the resin, so the tack-free time was faster than in examples 2 to 4.

In a third aspect, the present application provides the use of the low modulus sealant of the first aspect, the use comprising:

applying the low modulus sealant prepared in the first aspect to a bonded reinforced concrete substrate; or, applying the low modulus sealant prepared in the first aspect to a bonded metal substrate; alternatively, the low modulus sealant of the first aspect of the invention may be applied to a bonded wood substrate.

The sealant prepared by the method provided by the embodiment of the invention is a network-structure sealant which is formed by dehydration condensation of silanol functional groups and takes a silicon-oxygen bond as a connecting bond. The sealant can form chemical bonds with a concrete substrate, a metal substrate and a wood substrate respectively, and the strength of the chemical bonding generated based on the chemical bonds is far higher than that of the physical bonding, so that the sealant provided by the embodiment of the invention can be applied to bonding the concrete substrate, the metal substrate and the wood substrate.

It should be noted that the chemical bond formed between the sealant provided by the embodiment of the present invention and the concrete substrate (the concrete mainly contains Si) includes: Si-Si, C-Si, Si-O, C-O, etc.; the chemical bond formed between the sealant provided by the embodiment of the invention and the metal substrate (the metal can be Fe, Cu and the like) comprises the following components: Fe-O, Cu-O, etc.; the chemical bond formed between the sealant provided by the embodiment of the invention and a wood substrate (the main component of wood is C, H, O-based fiber) comprises the following components: C-Si, O-Si, C-O, etc.

In order to provide a better understanding of the invention to those skilled in the art, the use of the low modulus sealants of the present invention is illustrated by the application of examples 1-6 below.

Application example 1

The sealant prepared in the above example 2 was directly coated on the surface of the iron pipe substrate, and the adhesion strength was investigated. The results are shown in table 2 below.

Application example 2

The sealant prepared in the above example 2 was directly coated on the surface of the wood substrate, and the adhesive strength was investigated. The results are shown in table 2 below.

Application example 3

The sealant prepared in the above example 2 was directly coated on the surface of a concrete base material, and the adhesive strength thereof was investigated. The results are shown in table 2 below.

Application example 4 (comparative example)

The commercially available sealant is directly coated on the surface of the concrete base material, and the bonding strength of the concrete base material is researched. The results are shown in table 2 below. In the embodiment, the commercially available sealant is a polyurethane sealant produced by Hengshui Longqi rubber and plastic products, Inc.

Application example 5 (comparative example)

The commercially available sealant is directly coated on the surface of the wood substrate, and the bonding strength of the wood substrate is researched. The results are shown in table 2 below. In the embodiment, the commercially available sealant is a polyurethane sealant produced by Hengshui Longqi rubber and plastic products, Inc.

Application example 6 (comparative example)

The commercially available sealant is directly coated on the surface of the iron pipe base material, and the bonding strength of the sealant is researched. The results are shown in table 2 below. In the embodiment, the commercially available sealant is a polyurethane sealant produced by Hengshui Longqi rubber and plastic products, Inc.

TABLE 2 test results for the above application examples 1-6

Examples of the applications	1	2	3	4	5	6
							Bonding condition	No fracture	No fracture	No fracture	Partial fracture	Fracture of	Fracture of

Note: wood bonding, iron pipe bonding and concrete bonding means that the bonded samples are subjected to an external force damage test; the non-fracture refers to a damage experiment carried out under the action of external force, the sealant is broken from the bonding surface of the sealant before the base surface, the fracture refers to the cracking of the bonding surface, and the partial fracture refers to the cracking of the local bonding surface.

For simplicity of explanation, the method embodiments are described as a series of acts or combinations, but those skilled in the art will appreciate that the present invention is not limited by the order of acts, as some steps may occur in other orders or concurrently in accordance with the invention. Further, those skilled in the art will appreciate that the embodiments described in the specification are preferred embodiments and that the acts and elements referred to are not necessarily required to practice the invention.

The low-modulus sealant provided by the invention and the preparation method and application thereof are described in detail, the principle and the implementation mode of the invention are explained by applying specific examples, and the description of the examples is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.

Claims

1. The low-modulus sealant is characterized by comprising the following raw materials: silane modified polyether resin, a water absorbent, a plasticizer, a filler, a catalyst and an auxiliary agent.

2. The low-modulus sealant as claimed in claim 1, wherein in the low-modulus sealant, the silane modified polyether resin is 10 to 50 parts by weight, the water absorbent is 0.5 to 4 parts by weight, the plasticizer is 5 to 60 parts by weight, the filler is 20 to 70 parts by weight, the catalyst is 0.1 to 1 part by weight, and the auxiliary agent is 0.8 to 25 parts by weight.

3. The low modulus sealant according to claim 1, wherein the water absorbing agent is a powdered salt having a function of absorbing moisture, comprising: at least one of quick lime, soda lime, calcium chloride, magnesium chloride and phosphorus pentoxide.

4. The low modulus sealant according to claim 1 wherein said plasticizer comprises dioctyl phthalate and/or diisononyl phthalate.

5. The low modulus sealant of claim 1 wherein said filler comprises: basic fillers and/or neutral fillers;

6. The low modulus sealant of claim 1 wherein said catalyst comprises dibutyltin dilaurate.

7. The low modulus sealant of claim 1 wherein said adjuvant comprises: chain extenders, thixotropic agents, pigments, auxiliary crosslinking agents and light stabilizers;

8. The low modulus sealant of claim 7 wherein said chain extender comprises: at least one of dimethyl silicon glycol, dipropylene silicon glycol, polyether glycol, castor oil diol and dimethyl dimethoxy silane;

the thixotropic agent comprises oleophilic aerosil and/or polyamide wax;

the light stabilizer is a hindered amine light stabilizer.

9. A method of preparing a low modulus sealant according to any one of claims 1 to 8, said method comprising:

10. Use of a low modulus sealant according to any of the preceding claims 1 to 8, wherein said use comprises:

applying the low modulus sealant prepared according to any one of claims 1 to 8 to a bonded reinforced concrete substrate; or

Applying a low modulus sealant prepared according to any one of claims 1 to 8 to a bonded metal substrate; or

The use of a low modulus sealant prepared according to any one of claims 1 to 8 in the bonding of wood substrates.