FORM 2
THE PATENTS ACT, 1970
THE PATENTS f 1970) 003
COMPLETE SPECIFICATION
APPLICANT
The following specification particularly describes
the invention and the manner in which
it is to be performed

TITLE
Moisture-Curing Acrylate Sealant Compositions
TECHNICAL FIELD
The present invention relates to moisture-curing acrylate sealant compositions. More specifically, the present invention relates to a one-component moisture-curing acrylic sealant compositions for automotive powertrain applications with excellent compatibility with automotive transmission fluids. Further, it provides the method for preparing the moisture-curing acrylate sealant compositions.
BACKGROUND AND PRIOR ART
Moisture curable compositions are cured by the reaction of hydroxyl or hydrolysable groups bonded to silicon. These compositions are either prepared in the form of one-part compositions curable upon exposure to atmospheric moisture at room temperature or multiple (typically two) part compositions curable upon mixing at room temperature.
It is essential for a sealant composition to be capable of being applied as a paste to a joint between substrate surfaces where it can be worked, prior to curing, to provide a smooth surfaced mass which will remain in its allotted position until it has cured into an elastomeric body adherent to the adjacent substrate surfaces. Typically, sealant compositions are designed to cure quickly enough to provide a sound seal within several hours, however, at a speed enabling the applied material to be tooled into a desired configuration shortly after application.
The moisture curable compositions generally contain an organometallic compound as a catalyst for the reaction of the reactive groups of the polymer with the crosslinking agent. Although these groups react in the presence of moisture without a catalyst, an organometallic compound catalyst is generally required to promote curing of the composition, especially surface curing, in an acceptably short time.

These organometallic compounds can be problematic for human health and the environment.
The existing market has two dominating technologies; RTV Silicones (for example US2010/0225069A1) and Anaerobic Acrylic sealants (for example US7,728,092 B1) for face-sealing applications in engines, gearboxes, and differential joints. Various RTV silicone-based sealants are formulated in the adhesive world. However, the major drawback of all these sealants is that they have poor chemical resistance to all or either of the automotive transmission fluids. It has also been found during various studies that these silicone sealants deteriorate the properties of gear oil, engine oil, or various types of transmission oils whenever they tend to come in contact during service. This deterioration of properties of transmission fluids leads to foaming in oil which negatively impacts the performance of the component/assembly.
In the existing knowledge, acrylic sealants are designed to cure by free radical polymerization in presence of metal ions and the absence of air, thus, calling them as an anaerobic sealant. Acrylic sealants have good chemical resistance and heat resistance. However, in existing acrylic sealant curing is initiated only in absence of air. One of the major drawbacks of anaerobic sealant is its gap-filling ability and flexibility. Anaerobic acrylic sealants are limited in the application as they can be used to fill a gap of up to 0.25mm and are rigid in performance; hence, they cannot be used for joints requiring movement.
In view of the existing problems in present approaches, methods and compositions, it is desired to develop a moisture curing acrylate sealant composition that is capable to overcome the limitation of existing sealant compositions while being capable of improved gap-filling ability and flexibility. Further, it is desired to overcome the limitation of fluid incompatibility offered by existing RTV silicone sealants to various automotive fluids.

SUMMARY OF THE INVENTION
The present invention provides a moisture-curing acrylic sealant composition for automotive powertrain applications with excellent compatibility with automotive fluids and which cures in the presence of moisture at room temperature.
DETAILED DESCRIPTION OF INVENTION For the purposes of the following detailed description, it is to be understood that the invention may assume various alternative variations and step sequences, except where expressly specified to the contrary. Moreover, other than in any operating examples, or where otherwise indicated, all numbers expressing, for example, quantities of ingredients used in the specification are to be understood as being modified in all instances by the term "about". It is noted that, unless otherwise stated, all percentages given in this specification and appended claims refer to percentages by weight of the total composition.
The use of examples anywhere in this specification including examples of any terms discussed herein is illustrative only, and in no way limits the scope and meaning of the invention or of any exemplified term. Likewise, the invention is not limited to various embodiments given in this specification.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In the case of conflict, the present document, including definitions will control. It must be noted that, as used in this specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the content clearly dictates otherwise. Thus, for example, reference to a “solvent” may include two or more such solvents. The terms “preferred” and “preferably” refer to embodiments of the invention that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more

preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the invention.
As used herein, the terms “comprising”, “including”, “having”, “containing”, “involving”, and the like are to be understood to be open-ended, i.e., to mean including but not limited to.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiment of the invention only, and is not intended to limit the scope of the invention in any manner.
Thus, before describing the present invention in detail, it is to be understood that this invention is not limited to the following embodiment. The description of a particular embodiment and examples provided herein are only for the purpose of illustration and does not limit the scope of the invention to a particular embodiment.
The present invention provides for an acrylic sealant composition for face-sealing of joints in automotive powertrain applications. The composition comprises about 50-90% of intermediate 1, about 10-40% of intermediate 2, about 1.5 to 10% of intermediate 3 and about 5-15% of at least one curing agent such that the curing takes place at room temperature in presence of moisture.
The intermediate 1 consists of glycidyl methacrylate and acrylate rubber preferably in the ratio 3:1. The acrylate rubber is selected from at least one of active chlorine type, active carboxyl type, oxirane ring type, ACM, AEM and terpolymers of Ethelene.
The intermediate 2 consists of plasticizer and acrylic rubber preferably in a ratio of 77:23. The acrylic rubber component of intermediate 2 is selected from at least one

of active chlorine type, active carboxyl type, oxirane ring type, ACM, AEM and terpolymers of Ethelene. The plasticizer is a polyether ester-based plasticizer.
The intermediate 3 consists of silane and acrylic rubber preferably in the ratio of
70:30. The acrylic rubber component of intermediate 3 is selected from at least one
of active chlorine type, active carboxyl type, oxirane ring type, ACM, AEM and
terpolymers of Ethelene. The silane component of intermediate 3 is at least one
selected from 3-glycidoxypropyl trimethoxysilane, glycidoxyporpyl
triethoxysilane, glycidoxypropyl methyldiethoxysilane,
glycidoxypropylmethyldimethoxy silane.
The curing agent is selected from at least one of monooxazolidine, bisoxazolidine or its derivatives. In a preferred embodiment, the curing agent is Incozol.
In another embodiment of the present invention, the acrylic sealant composition further comprises of other ingredients such as reinforcing agents like carbon black, inorganic fillers, thickening agent like fumed silica, catalysts like Dibutyltin dilaurate (DBTL) or other TIN catalysts well known in the art, inhibitors like 4-methoxyphenol (MEHQ) and scavengers like Vinyltriethoxysilane (VTMS).
The following examples are provided to better illustrate the claimed invention and are not to be interpreted in any way as limiting the scope of the invention. All specific materials, and methods described below, fall within the scope of the invention. These specific compositions, materials, and methods are not intended to limit the invention, but merely to illustrate specific embodiments falling within the scope of the invention. One skilled in the art may develop equivalent materials, and methods without the exercise of inventive capacity and without departing from the scope of the invention. It is the intention of the inventors that such variations are included within the scope of the invention.

EXAMPLES Example 1: :
Sr. no Ingredient Percentage (%)
1 Intermediate 1 50-90
2 Intermediate 2 10-40
3 Intermediate 3 1.5-10
4 Carbon Black 10-30
5 Fumed Silica 5-20
6 Incozol 5-15
7 Dibutyltin dilaurate (DBTL) 0.5-5
8 4-methoxyphenol (MEHQ) 0.5-5
9 Vinyltriethoxysilane (VTMS) 0.5-5
The constituent of the intermediates in the composition are provided below:
*Intermediate 1 – Glycidyl methacrylate + acrylate rubber *Intermediate 2 – Plasticizer + Acrylic rubber *Intermediate 3 – Silane + Acrylic rubber
The process for producing one-component moisture-curing acrylic sealant composition comprises: preparing the three intermediates. The Intermediate 1 is prepared by combining Glycidyl methacrylate and acrylate rubber. The Intermediate 2 is prepared by plasticizer and acrylic rubber. The Intermediate 3 is prepared by silane and acrylic rubber. Each intermediate is prepared by mixing the ingredients at 90-100°C in presence of a stabilizer, Butylated hydroxytoluene (BHT).
This is followed by adding fumed silica and carbon black and mixing with vacuum degassing. Thus, adding the components to the vacuum mixer individually in succession, is performed followed by degassing the mixture; wherein the moisture-curing acrylic sealant composition is formed. VTMS is added further after a homogenous mixture is formed. Now Incozol is added and again mixing is

performed. At last, DBTL is added, and after mixing, the sealant is packed in air¬tight containers.
PERTINENT TEST DATA & LAB REPORTS
Experimental data provided below shows that invented composition is superior.
Example 2: Properties of Invented present sealant composition
Properties Optimized Composition 1
General Properties
Color Grey
Viscosity Non-Sag
Specific Gravity 1.25
Cure characteristics, @25±2 ᵒC @Relative Humidity 55±5 %
Skin Over Time 60-70 min
Tack Free time 70-80 min
Full Cure time 14 days
Polymer Characteristics, Cured for 14days@25±2 ᵒC @Relative
Humidity 55±5 %
Tensile Strength, ASTM D412 1.1 N/mm²
Elongation, ASTM D412 ≥100%
Hardness, Shore A, ASTM D2240 25-30
Adhesive Strength, Lap Shear Strength,
Cured for 14days @25±2 ᵒC @Relative Humidity 55±5 %
Mild Steel – Mild Steel 1.14
Aluminium-Aluminum 2.5
Mild Steel - Aluminium 1.21

to evaluate the performance of sealant properties after exposing the substrates to
desired hot temperature in air for a defined time and then testing at room
temperature ie. 25±2 °C.

Test Process:
1. Cured for 14 days at 25±2 °C
2. Aged at 150°C in hot air for 1000hrs
3. Tested at room temperature @25±2 °C

Properties Unit Substrate Standard Optimized Composition 1
Polymer Characteristics
Tensile Strength N/mm2 Polymer strip ASTM D412 2.76
Elongation % Polymer strip ASTM D412 82
Hardness, Shore D - Polymer strip ASTM D412 37
Adhesive Strength
Lap Shear Strength N/mm2 MS-MS ASTM D1002 3.91

AL-AL
6.53

AL-MS
3.66
Example 4: Test Results - Chemical Resistance Test System: Chemical resistance test is conducted to evaluate the performance of sealant properties after exposing the substrates at desired fluid-temperature-time and then testing at room temperature ie. 25±2 ᵒC.
CRT 1-Engine Oil Aging
Test Process:
1. Cured for 14 days at 25±2 ◦C
2. Aged at 150 ᵒC in engine oil for 1000hrs
3. Tested at room temperature @25±2 ◦C

Properties Unit Substrate Standard Optimized Composition 1
Polymer Characteristics
Tensile Strength N/mm2 Polymer strip ASTM D412 4.75
Elongation % Polymer strip ASTM D412 84
Hardness, Shore D - Polymer strip ASTM D412 39
Adhesive Strength, Lap Shear Strength
Lap Shear Strength N/mm2 MS-MS ASTM D1002 4.23

AL-AL
8.76

AL-MS
6.52
Observation: Sealant retains more than 100% Adhesives strength after exposure to engine oil for 1000hrs at 150 ᵒC.
CRT 2-Gear Oil Aging-85W140-GL5 Grade
Test Process:
1. Cured for 14 days at 25±2 ◦C
2. Aged at 150 ᵒC in 85W140 gear oil for 1000hrs
3. Tested at room temperature @25±2 ◦C

Properties Unit Substrate Standard Optimized Composition 1
Polymer Characteristics
Tensile Strength N/mm2 Polymer strip ASTM D412 5.36
Elongation % Polymer strip ASTM D412 87
Hardness, Shore D - Polymer strip ASTM D412 34
Adhesive Strength, Lap Shear Strength
Lap Shear Strength N/mm2 MS-MS ASTM D1002 5.83

AL-AL
7.95

AL-MS
6.65

Observation: Sealant retains more than 100% Adhesives strength after exposure to gear oil 85W140-GL5 Grade for 1000hrs at 150 ᵒC.
CRT 3-Gear Oil Aging-85W90-GL5 grade
Test Process:
1. Cured for 14 days at 25±2 ◦C
2. Aged at 150 ᵒC in 85W90 gear oil for 1000hrs
3. Tested at room temperature @25±2 ◦C

Properties Unit Substrate Standard Optimized Composition 1
Polymer Characteristics
Te nsil e St rengt h N/ mm2 Polymer strip ASTM D412 3.98
Elongation % Polymer strip ASTM D412 81
Hardness, Shore D - Polymer strip ASTM D412 32
Adhesive Strength, Lap Shear Strength
Lap Shear Strength N/mm2 MS-MS ASTM D1002 6.96

AL-AL
7.33

AL-MS
5.84
Observation: Sealant retains more than 100% Adhesives strength after exposure to gear oil 85W90-GL5 Grade for 1000hrs at 150°C.
Advantageously, the acrylic sealant composition is compatible with different automotive fluids. It does not react with gear oil/engine oils both in cured and uncured state. The excellent compatibility of the present composition with automotive fluids has resulted in no foaming tendency of automotive fluids.

Consequently, the seal as well as the automotive fluid has a longer life. Even the component life is increased.
The present sealant composition provides strong sealing and adhesion while being highly flexible and remarkable in gap filling ability. More specifically, the composition has excellent sealing and adhesion with the cast iron to cast iron, aluminium to aluminium and cast iron to aluminium flange joints used in powertrain flange sealing applications.
The sealant composition has good instant sealing ability i.e. after assembly of two flanges, it gives pressure resistance of 0.3 to 0.5 bar immediately in uncured condition and high-pressure resistance when cured completely. Moreover, the invented composition does not require presence of metal ions and absence of air to cure unlike the anaerobic acrylic sealant.
The slow-curing nature of the present sealant composition provides an advantage of having moderate work life thus, enabling more time to assemble the flange on the production line thereby limiting shimming effect.
The present sealant composition has excellent retention in adhesive strength and polymer properties when aged in hot air such as engine oil and gear oils at 150°C. It combines the benefits of anaerobic sealants i.e. strength and the ability of Silicone sealants i.e. flexibility while at the same time having remarkable gap-filling ability which was a major drawback in silicone and anaerobic sealants when considered one at time. This major advantage has opened the possibility of using the present sealant composition in multiple applications. Therefore, it can be used in place of anaerobic and silicone sealants rendering it as a universal sealant thereby reducing the requirement of multiple types of sealants on the same line, which raises multiple compatibility and maintenance issues.

As stated herein above, the example embodiments of the present inventive concepts have been described are for illustrative purposes only and cannot limit the scope of the invention. A person skilled in the art will appreciate that various modifications and other equivalent embodiments are possible from those described herein in this document.

We Claim:
1. An acrylic sealant composition for face-sealing of joints in automotive powertrain applications, said composition comprising about 50-90% of intermediate 1, about 10-40% of intermediate 2, about 1.5 to 10% of intermediate 3, about 5-15% of at least one curing agent such that the curing takes place at room temperature in presence of moisture.
2. The acrylic sealant composition for face-sealing of joints in automotive powertrain applications as claimed in claim 1, wherein intermediate 1 consists of glycidyl methacrylate and acrylate rubber used in the ratio 3:1.
3. The acrylic sealant composition for face-sealing of joints in automotive powertrain applications as claimed in any of the preceding claims wherein acrylate rubber of intermediate 1 is selected from at least one of active chlorine type, active carboxyl type, oxirane ring type, ACM, AEM and terpolymers of Ethelene.
4. The acrylic sealant composition for face-sealing of joints in automotive powertrain applications as claimed in any of the preceding claims wherein Intermediate 2 consists of plasticizer and acrylic rubber in a ratio of 77:23.
5. The acrylic sealant composition for face-sealing of joints in automotive powertrain applications as claimed in any of the preceding claims wherein acrylic rubber of intermediate 2 is selected from at least one of active chlorine type, active carboxyl type, oxirane ring type, ACM, AEM and terpolymers of Ethelene.

6. The acrylic sealant composition for face-sealing of joints in automotive powertrain applications as claimed in any of the preceding claims wherein plasticiser is a polyether ester-based plasticizer.
7. The acrylic sealant composition for face-sealing of joints in automotive powertrain applications as claimed in any of the preceding claims wherein Intermediate 3 consists of silane and acrylic rubber in the ratio of 70:30.
8. The acrylic sealant composition for face-sealing of joints in automotive powertrain applications as claimed in any of the preceding claims wherein acrylic rubber of intermediate 3 is selected from at least one of active chlorine type, active carboxyl type, oxirane ring type, ACM, AEM and terpolymers of Ethelene.
9. The acrylic sealant composition for face-sealing of joints in automotive powertrain applications as claimed in any of the preceding claims wherein silane comprised in intermediate 3 is at least one selected from 3-glycidoxypropyl trimethoxysilane, glycidoxyporpyl triethoxysilane, glycidoxypropyl methyldiethoxysilane, glycidoxypropylmethyldimethoxy silane.
10. The acrylic sealant composition for face-sealing of joints in automotive powertrain applications as claimed in any of the above claims wherein the curing agent is selected from at least one of monooxazolidine, bisoxazolidine or its derivatives.
11. The acrylic sealant composition for face-sealing of joints in automotive powertrain applications as claimed in any of the above claims wherein the curing agent is Incozol.

12. The acrylic sealant composition for face-sealing of joints in automotive powertrain applications as claimed in any of the preceding claims further comprises of reinforcing agents, scavengers, thickening agents and inhibitors.