FORM 2
HE PATENTS ACT, 1970
(39 of 1970) PATENTS RULES, 2003
COMPLETE SPECIFICATION
TITLE OF THE INVENTION
ENERGY SURFACE MATERIALS

APPLICANT Pvt
of W-27, MIDC, ndustrial Area, Kalmeshwar, Nagpur-441 501, Maharashtr, India; India
following specification particularly describes the invention and the manner in which it is to be performed

UNIVERSAL RAPID CURING TWO COMPONENT ADHESIVE SYSTEM TO BOND LOW ENERGY SURFACE MATERIALS
TECHNICAL FIELD
5 The present invention relates to two-component universal rapid curing high strength
structural adhesive system to bond low energy surface materials. In particular, the
present invention relates to an adhesive system comprising an adhesive component
capable of free radical polymerisation and an activator component capable of
forming free radicals in which the adhesive system can be applied without any
10 surface pretreatment prior to bonding such as application of primer, corona
treatment, plasma treatment, flame treatment or such other surface pretreatments.
BACKGROUND AND PRIOR ART
Low energy surfaces such as polyolefins i.e. polyethylene, polypropylene, nitrile
15 rubber, polyisoprene, polyamides, and copolymers thereof and metals like
galvanised metals, special aluminium alloys, e-coated steel are well known to be difficult to bond to each other and to other surfaces using adhesive bonding technology since they have a few active bonding sites available at the free surfaces.
20 Bonding low energy surfaces by including surface pre-treatments such as flame
treatments, plasma treatments, oxidation, sputter etching, corona discharge or primer treatments with a high surface energy material is well known. Such treatments disrupt the bonds at the surface of the low energy material providing sites which are reactive and which can participate in bonding reactions with
25 adhesive materials. Such surface pre-treatments are usually undesirable, in that they
add costs to the process, they are not particularly reproducible in their results, and the effect of the pre-treatments wears off with time. Therefore, the pre-treated surfaces must be re-pre-treated if they are not bonded within a reasonable period of time.
30
2

Prior art US7683132 has addressed this concern by disclosing an accelerated
organo-borane initiated polymerizable composition. The invention is a two-part
polymerizable composition comprising in one part an organo-boron compound
capable of forming free radical generating species and in the second part one or
5 more compounds capable of free radical polymerisation. 20 to about 30 parts by
weight based on the weight of the second part comprises i) a halogenated polyolefin
having halo-sulfonyl groups or ii) a mixture of a halogenated polyolefin and an
organic sulfonyl halide. The second part may further contain a compound capable
of causing the organo-boron compound to form free radical generating species upon
10 contacting the two parts. The first part may further comprise one or more
compounds capable of free radical polymerisation.
Another prior art US7408012 discloses adhesives bonding systems having adherence to low energy surfaces. The document discloses a polymerizable
15 composition for bonding a low surface energy substrate to a similar or different
substrate, comprising: a) at least one free-radically polymerizable monomer component; b) an effective amount of an initiator system for initiating polymerisation of the free-radically polymerizable monomer, said initiator system comprising: alkylated boron-hydride or tetra-alkyl borane metal or ammonium
20 salts.
Whereas US7348385 discloses acrylate/methacrylate adhesive initiated by CSPE,
an adhesive formulation including an acrylate monomer and/or a methacrylate
monomer, a chloro-sulfonated polymer resin, and a reducing agent. The adhesive
25 also includes a cycloheteroatom zirconate or a cycloheteroatom titannate, which is
utilised as a cure profile regulator. Further, the adhesive includes toughening agent copolymers having a very low Tg to increase impact strength of the cured adhesives at low temperatures.
30 In some prior art cases, solvent based adhesives are the systems of choice to
overcome the challenge of adhering onto low surface energy materials, since the
3

solvent can partially melt the plastic material of the film, therefore helping to obtain
slightly higher performance. However, the performance gains are far from
satisfying and it is furthermore more desirable to use solvent free adhesive systems
for environmental and toxicity reasons. Further, all formulations disclosed in the
5 prior art can bond galvanised metals and low energy substrates like polyproylene,
with slower curing and lower bond strength which is not user friendly. The prior art compositions exhibit good bonding strength only after 4-6 hours of curing.
Because of this, separate adhesives systems are required to be used for metals and
10 plastics with difficult mix ratios. Most of the time extent of curing is very less which
affect the ultimate bonding strength of the composition. The compositions of the
prior art cure at a slower rate at ambient temperature and development of strength
is very slow on polyolefins and as such low energy surface metals like e-coated
steel and galvanised metal substrates cannot be bonded. Many prior art
15 compositions polymerise more slowly than desired level i.e. more than 10 minutes
pot life. Development of strength is slower than desired and some of these prior art compositions even require surface treatment. Also, the thermal stability is not found to be good at elevated temperature.
20 Also, for a two-part adhesive to be most easily used in commercial and industrial
environment, it is helpful if the volume ratio at which the two parts are combined should be convenient whole number. This facilitates application of the adhesive with conventional, commercially available dispensers.
25 In view of the existing problems, it is an object of the present invention to provide
for adhesives which are not only solvent-free but also show improved adhesiveness on low surface energy films. It is another object of the present invention to provide for adhesives which do not require surface pre-treatments such as priming, corona discharge, plasma treatments or flame treatments which not only add costs to the
30 entire procedure but also makes it more tedious and time and energy consuming.
4

SUMMARY OF THE INVENTION
In keeping with the objectives mentioned hereinabove, the present invention
comprises of a two-component, rapid curing, high strength adhesive formulation to
bond low energy surface materials in which there is an adhesive component capable
5 of free radical polymerisation and an activator component capable of forming free
radicals and the adhesive formulation can be applied without any surface pretreatment such as application of primer, corona treatment, plasma treatment, flame treatment or such other surface pretreatments.
10 BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
The various aspects of the present invention will be apparent and more readily appreciated from the following description of the example embodiment taken in conjunction with the accompanying drawings in which: Figure 1 depicts the test cycle for PV1200
15
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
20 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.
25
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.
30
5

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
5 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,
10 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,”
15 “involving,” and the like are to be understood to be open-ended, i.e., to mean
including but not limited to.
Cohesive Failure (CF) is a term used to determine the proper bonding of adhesive
and it means that failure occurred with the layer of adhesive to remain on both the
20 surfaces fracturing the adhesive bond within.
Substrate failure (SF) occurs when external loads exceed the strength of one or the
other substrates. When this happens, the substrate reaches the point of deformation
and eventually its yield point, resulting in failure. This type of failure does not
25 indicate failure of the adhesive; rather, if the external loads to which the assembly
was subjected are reasonable proxies for a real-world condition, a stronger substrate is needed.
Adhesive failure (AF), or delamination, is one of the most common types of failure
30 mechanisms. There the two dissimilar materials detach from each other. The failure
6

can happen between the adhesive and either of the two substrates, it is bonding together.
Unless defined otherwise, all technical and scientific terms used herein have the
5 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 a particular embodiment of the invention only, and is not intended to limit the scope of the invention in any manner.
10 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.
15 In one aspect, the present invention provides for a universal rapid-curing, two-
component adhesive formulation to bond low energy surface materials comprising an adhesive component capable of free radical polymerisation and an activator component capable of forming free radicals. The adhesive component comprises of an impact and bond strength modifier, acrylate/methacrylate monomers, Lewis
20 acid, rigid thermoplastic resin, rheology modifier, peroxy benzoate and inhibitor.
The effective component is the impact and bond strength modifier is a thermoplastic resin-based core shell rubber and is selected from High rubber graft and methyl methacrylate butadiene styrene (MBS). The High Rubber Graft co-polymer comprises core shell rubber and grafted elastomer. The core shell rubber consists
25 of polybutadiene as shell and styrene acrylonitrile co-polymer as the core. The rigid
thermoplastic resin is added in the adhesive component to enhance the glass transition temperature (Tg) and toughness of the adhesive formulation when cured.
In the invented adhesive formulation, the activator component comprises of organo-
30 borane amine complex agent, catalyst activator, a pyridine accelerator, chiral
compound, nano-fillers and a green bio plasticiser. The catalyst activator is selected
7

from Triethylborane -diaminopropane (TEB DAP) and Boron-Tributyl-3-Methoxypropanamine + 3 methoxypropanmine (TNBB-MOPA).
The invented adhesive formulation displays excellent adhesion to low energy
5 surfaces like the virgin and reinforced plastics, glass, steel and aluminium alloys.
In particular, the low surface energy materials are high density polyethylene, low
density polyethylene, virgin and reinforced plastics, ABS, ABS-PC alloy, PC, PBT,
CFRP, FRP, polypropylene, nylon, polycarbonate and metals like E-coated steels,
galvanised metals like Z-90, Z-70, Z-60, stainless steel, KTL E-coated steel, GB
10 Mild steel, glass, and aluminium alloys.
An important feature of the adhesive composition of the present invention is that it
can be applied to the substrate without any surface pre-treatment like application of
primer, corona treatment, flame treatment, plasma treatment and the like. Adhesion
by present invention is promoted by reaction catalyst that produces radical
15 initiators. These radicals may then extract hydrogen from low energy surface and
creates sites for adhesion creating reactive bonding.
EXAMPLES
The present invention is hereinafter illustrated by way of an exemplary
20 embodiments for better understanding but is not intended to limit the scope of the
disclosure. While they are typical of those that might be used, other procedures,
methodologies or techniques known to those skilled in the art may alternatively be
used. In this regard, the present example embodiment may have different forms and
should not be construed as being limited to the descriptions set forth herein.
25 Accordingly, the example embodiments are merely described below for the purpose
of explanation only.
The optimised adhesive formulations 1 and 2 of the present invention are as follows-
8

Ingredients Optimised formulation 1 Optimised formulation 2
Adhesive components
Acrylate/methacrylate monomer 63 63
Carboxylic acid 3.0 3.0
High Graft Rubber 28.5 28.5
Fumed silica Hydrophilic 0.4 0.4
Inhibitor 0.6 (4% in monomer) 0.6 (4% in monomer)
Peroxy benzoate 0.5 0.5
Rigid thermoplastic resin 4.0 4.0
Activator components
Bio-based plasticiser 25 25
Nano fillers 68 68
Pyridine accelerator 2.0 2.0
TEB-DAP 5.0 00
TNBB-MOPA 00 5.0
Chiral compound 0.005 0.005
The examples are prepared by methods known to a person skilled in the art.
Optimised formulations 1 and 2 were evaluated for work time, determination of pot
5 life by development of strength, viscosity, lap shear at room temperature, lap shear
at 90°C/ 500 hours, lap shear at 120°C/24 hours, thermal stability at 62°C for 5 days & at 23°C for 168 hours, Humidity & Heat Aging (- 40°C to 80°C) Salt Spray Resistance, & development of strength on various low energy substrates.
10
9


10

Thermal stability testing
Uncured samples were subjected to 82±1°C for 8 hours and no change in viscosity and no polymerisation was observed. Both formulations remained stable after 24 hours. 5
Both the formulations showed even better performance and stability when subjected to 62±1°C and were found to be stable even after 5 days without having any effect on the final product performance in bonding the various low energy substrates and metals. 10
Table 2 – Thermal Stability Test Results for Optimised Formulation 1

Day @ Temp Pot life (mins) Lap Shear Strength (LSS), PP-PP

30 mins 60 mins 120 mins 24 hours
1day @ 62±1°C 3.5 0.43 (CF) 2.05 (CF) 5.54 (SF) 6.46 (SF)
2day @ 62±1°C 5 0.55 (CF) 3.42 (CF) 5.03 (CF) 5.14 (SF)
3day @ 62±1°C 9 0.25 (CF) 1.88 (CF) 4.7 (CF) 6.25 (SF)
4day @ 62±1°C 8.5 0.06 (CF) 1.8 (CF) 4.59 (CF) 6.54 (SF)
5day @ 62±1°C 8 0.15 (CF) 0.39 (CF) 1.96 (CF) 6.52 (SF)
Table 3– Thermal Stability Test Results for Optimised Formulation 2

Day @ Temp Pot life (mins) Lap Shear Strength (LSS), PP-PP

30 mins 60 mins 120 mins 24 hours
1day @ 62±1°C 4 2.55 (CF) 3.74 (SF) 7.41 (SF) 7.02 (SF)
2day @ 62±1°C 4 2.20 (CF) 2.54 (CF) 3.04 (SF) 3.14 (SF)
3day @ 62±1°C 5 1.82 (CF) 4.39 (SF) 5.41 (SF) 6.14 (SF)
4day @ 62±1°C 4 1.74 (CF) 1.83 (CF) 5.50 (SF) 6.19 (SF)
5day @ 62±1°C 4.5 1.50 (CF) 1.80 (CF) 4.1 (SF) 5.1 (SF)
15 Uncured samples were subjected to 90±1°C for 20 days. Slight change in viscosity
by less than 10 % relative to initial viscosity was observed. Pot life, mechanical strength, bonding capability of low energy surfaces and development of strength
11

for polypropylene remained within 90% relative to the initially formulated samples substrates during the test period. Further, product performance and lap shear strength are found to be within 90% even after aging the sample at 90°C for 20 days. 5
Optimised formulations showed even better performance and stability when
subjected to 120±1°C/24 hours. Both optimised formulations 1 and 2 were observed
to be stable for more than 90 days, without having a substantive performance
decrease. Whereas prior art products, Reference samples 1 and 2 failed showing
10 Adhesive failure (AF).
Table 4 – Thermal stability testing data

15 Thermal Cycle PV 1200 Testing:
This thermal testing is an important test to determine environmental resistance for various automotive applications. This Test Specification describes an environmental cycle test (elevated temperature/low temperature cycle) for testing units, e.g. vehicle parts in the engine compartment. The behaviour of the units
20 and/or parts during environmental cycle stressing by means of cycling temperature
and moisture is assessed here (e.g. susceptibility to cracks, deformation, separation of the composite, plastic, bonded material, etc.). The purpose of the test specification (Temperature -40°C to 80°C) is to uncover component and bond
12

weaknesses in a short-term test with accelerated time effect but not to define general component requirement for continuous operations.
Description: PV 1200 without restriction. With reference to figure 1, the
5 temperature was regulated with a tolerance of ± 2.0°C and relative humidity with a
tolerance of ± 5%. The climatic chamber was already set to room temperature
(23°C) and 30% rel. humidity. The test specimens were inserted after setting an
environmental chamber at 23°C and 30% relative humidity. The holding times were
always maintained. The heating and cooling phases could be varied according to
10 the performance capability of the climatic chambers used.
One cycle lasted for 720 min (12 h) and comprised the following temperature and
humidity profiles -
60 min heating phase to +80°C and 80% rel. humidity,
15 240 min holding time at +80°C and 80% rel. humidity,
120 min cooling phase to -40°C, when freezing point was reached: approx. 30% relative humidity, air humidity remains un-regulated as of T < 0°C (depending on the system, humidity regulation can also be suspended as of T < 10°C), 240 min holding time at -40°C, air humidity remained uncontrolled,
20 60 min heating phase to +23°C, rel. humidity was regulated to 30% as of T = 0°C
All the samples were subjected to the PV 1200 thermal cyclic testing and found that optimised formulations 1 and 2 could sustain over 20 cycles of the test whereas the reference samples failed to complete even 5 cycles of this test.
13
25 Table 5 – Thermal cycle study data


Strength Development for Optimised Formulations Relative to Reference Sample on various low energy substrates that included metals & plastics:
Duplicate lap joints were formed between LSS strips of various low substrate
materials having a thickness of 3.02 mm and an adhesive thickness of between 0.03
5 mm and 0.06 mm at a temperature of 23.5°C. No prior surface preparation was
performed. The coupon dimensions were 101.6 mm x 25.4 mm x 3.35 mm with an overlap of 25.4 mm x 12.5 mm with a ramp rate of 50mm per minute. The strips were bonded with optimised formulations 1 & 2 and the reference samples of 1 & 2. The single lap shear strength of both optimised formulations was compared to
10 reference samples 1 and 2 on various substrates as seen in Table 6 below. It was
observed that the reference samples failed due to not bonding at all or due to adhesive failure. Whereas optimised formulations 1 and 2 of present invention showed excellent bonding with particularly stronger bonds for polypropylene, high density polyethylene, ABS, nylon, CFRP, FRP, galvanised metal Z-90 and Z-60,
15 aluminium, stainless steel, E-coated steel, GB Mild steel.
14


5

The room temperature strength on neat polypropylene substrates is provided below for optimised formula 1 and 2 variants and reference samples 1 and 2. Single Lap shear strength on polypropylene as a function of time was measured.
15

Determination of Pot life by Development of Strength: Overlap samples were prepared with PP strips making a bond of the adhesives system every after 30 sec 5 up to 4 min till the time pot life was achieved and later these bonded samples were tested for LSS values after 24 hrs curing.

Table 8 - Determil] at ion of Pot life by development of strength
16

The LSS coupons were cured after bonding at 60°C, 70°C, 80°C for 10 mins and then again10 mins at room temperature after taking out coupons from the heating oven. The results are tabulated as follows –
17


18

Salt Spray Test: Salt spray test was performed on the bonded specimen using LSS
coupons to determine the resistance of salt spray environment over the bond
strength. LSS was found to be approximately the same after exposure for two weeks
in salt spray chamber as compared to room temperature value. This indicated that
5 salt exposure did not hamper adhesion over galvanized substrates.

Advantageously, the adhesive formulation of present invention demonstrates
10 excellent bond strength and cures fast in comparison with existing products. It
passes the 20 cycles of PV 1200 test which is crucial from automotive application
point of view. It exhibits excellent bond strength over 7 days exposure to salt spray
test. Development of strength and fixture time of adhesive disclosed for a wide
variety of low energy surfaces tested and disclosed hereinabove are found to be
15 better than those in disclosed in prior art. Prior art compositions do not bond with
significantly high strength or do not bond at all to low energy surface metals. The
adhesive formulations of the present invention exhibit excellent bonding strength
leading to Substrate Failure (SF) over a period of 3 hours with respect to low energy
surface plastics. In case of low energy surface metals, it shows Cohesive failure at
20 bond thickness ranging from 0.5 to 5mm.
19

The formulations of present invention are far more superior to the existing prior art
products in terms of thermal stability over wide range of temperature where the
existing prior art products get destabilised at higher temperature, the adhesive
formulations of present invention can be stored at room temperature without any
5 refrigeration or freezing aids.
Moreover, the adhesive formulations of present invention are seen to be capable of
bonding a wide spectrum of low energy surface plastics and metals including virgin
and reinforced polypropylene, polyethylene, high density polyethylene, ABS, ABS-
10 PC alloy, PC, CFRP, FRP, E-coated steel, galvanised metals like Z-60, Z-90,
aluminium alloys, glass etc. Therefore, the invented adhesive formulations have
universal application.
Another important advantage of the present invention is that it can be directly
15 applied on any low energy substrates without the need of any surface pre-treatment
such as application of primer, flame treatment, plasma treatment, corona treatment and the like.
Further, the adhesive formulations of present invention are easily dispensable due
20 to moderate viscosities, excellent hardness of the composition imparts shrink
resistance at lower temperatures.
The present invention is unique in terms of using the thermoplastic resin to achieve
higher bond strength in acrylate based thermoset adhesive system. The invented
25 adhesive formulations find usage mainly in automotive assembly, aerospace,
industrial piping, transportation and construction lines where fast development of strength is required and many other applications like appliance industries, automotive fasteners, recreation, marines, toys, building blocks etc.
30 The present invention is illustrated hereinabove by way of an exemplary
embodiment read along with annexed diagrams for better understanding but is not
20

intended to limit the scope of the disclosure. While they are typical of those that might be used, other procedures, methodologies or techniques known to those skilled in the art may alternatively be used. Accordingly, the example embodiments are merely described for the purpose of explanation only. 5
21

We claim:
1. A universal rapid-curing, two-component adhesive formulation to bond low
5 energy surface materials comprising an adhesive component capable of free
radical polymerisation and an activator component capable of forming free radicals in which said adhesive system is applied without any surface pre-treatment like application of primer, corona treatment, flame treatment, plasma treatment or such other treatment. 10
2. The universal rapid-curing, two-component adhesive formulation to bond
low energy surface materials as claimed in claim 1, wherein the ratio of the
adhesive: activator is 10:1.
15 3. The universal rapid-curing, two-component adhesive formulation to bond
low energy surface material as claimed in claim 1, wherein the low energy surface materials include virgin and reinforced plastics, glass, steel and aluminium alloys.
20 4. The universal rapid-curing, two-component adhesive formulation to bond
low energy surface materials as claimed in any of the preceding claims wherein the adhesive component comprises of an impact and bond strength modifier, acrylate/methacrylate monomers, Lewis acid, rigid thermoplastic resin, rheology modifier, peroxy benzoate and inhibitor.
25
5. The universal rapid-curing, two-component adhesive formulation to bond low energy surface materials as claimed in any of the preceding claims wherein the activator component comprises of organo-borane amine complex agent, catalyst activator, a pyridine accelerator, chiral compound,
30 nano-fillers and a green bio plasticiser.
22

6. The universal rapid-curing, two-component adhesive formulation to bond
low energy surface materials as claimed in any of the preceding claims
wherein the catalyst activator is selected from Triethylborane -
diaminopropane (TEB DAP) and Boron-Tributyl-3-Methoxypropanamine
5 + 3 methoxypropanmine (TNBB-MOPA).
7. The universal rapid-curing, two-component adhesive formulation to bond
low energy surface materials as claimed in any of the preceding claims
wherein the impact and bond strength modifier is a thermoplastic resin-
10 based core shell rubber and is selected from High rubber graft and methyl
methacrylate butadiene styrene (MBS).
8. The universal rapid-curing, two-component adhesive formulation to bond
low energy surface materials as claimed in claim 3, wherein the low surface
15 energy materials are high density polyethylene, low density polyethylene,
virgin and reinforced plastics, ABS, ABS-PC alloy, PC, PBT, CFRP, FRP, polypropylene, nylon, polycarbonate and metals like E-coated steels, galvanised metals like Z-90, Z-70, Z-60, stainless steel, KTL E-coated steel, GB Mild steel, glass, and aluminium alloys.
20
Dated this 28 day of March 2024
~Digitally signed~
Arindam Paul
REG.NO:IN/PA-174
of De Penning & De Penning
Agent for the Applicants