FIELD OF THE INVENTION

The present invention is in the field of flexible adhesives for gluing, in particular in the construction of trucks, buses, trains and the like, more in particular for adhering a relatively large workpiece. The present invention also relates to a product comprising said adhesive, and a use of said adhesive.

BACKGROUND OF THE INVENTION

In the construction industry, and in particular in the construction of trucks, buses, trains and the like, there is a need for flexible adhesives for gluing. For example, a flexible glue for adhering large parts to one and another, or even series of parts, typically of different types of materials, for which the glue (or adhesive) hardens quickly once the bond has been made. In view of the large parts, adhesives are required to have a long open time on the one hand and, on the other hand, have a rapid strength build-up after the open time has elapsed and have good adhesive built-up. The adhesive must also meet further technical properties as required. Examples thereof are elasticity, strength, durability, adhesion, and being free of tackiness. Additionally, such as when applied in the field of vehicles, leakage of water trough punctured sealants may cause severe damage, which leakage is to be prevented from happening.

Some documents may be referred to. DE 102009027 357 A1 recites a two-component adhesive or sealant masses (K) with a first component (Kl) containing silane-terminated pre polymers (A) which have end groups of the general formula (II) -0-CO-NH-(CH)-SiR(OR), where R R are independently hydrocarbon radicals having 1-18 carbon atoms or co-oxaalkyl- alkyl radicals having a total of 2-20 carbon atoms, x is 2 or 3 and y is a number from 1 to 10, and a second component (K2) containing water, with which Provided that at least 50% of all prepolymer molecules (A) in the backbone of the prepolymer chain have no additional ure thane or urea units, DE 102006022095 A1 recites polymer blends (P) which A) alkoxysilane-terminated polymers (A) having at least one end group of the formula (1) -A- (CH2)m-SiR l _a (OR ² )3-a, where A is a divalent linking group selected from -0-, -S-, -(R ³ )N-, - 0-CO-N(R ³ )-, -N(R ³ )-CO-0-, -N(R ³ )-CO-NH-, -NH-CO-N(R ³ )-, -N(R ³ )-CO-N(R ³ )-, R ¹ is an optionally halogen-substituted alkyl, cycloalkyl, alkenyl or aryl radical with 1- 10 carbon atoms, R ² is an alkyl radical having 1-6 carbon atoms or an omega-oxaalkyl-alkyl radical having a total of 2-10 carbon atoms, R ³ is hydrogen, an optionally halogen-substituted cy clic, linear or branched Ci- to Cis-alkyl or alkenyl radical or a Ce- to Cis- aryl radical, a is an integer from 0 to 2 and m is an integer from 1 bi s is 6, B) pyrogenically produced or precipi tated silica with a BET surface area of at least 50 m2/g and C) contain a catalyst with at most 0.05% by weight of amino compounds and no other fillers. It is therefore an object of the present invention to provide an adhesive which overcomes one or more of the above disad vantages, without jeopardizing functionality and advantages. SUMMARY OF THE INVENTION

The present invention relates to a two component flexible adhesive for gluing com prising a first and second component, the first component, comprising (la) 0.1-50 wt.% of at least one first silane-terminated (Si(ORi)2R3) polymer (STP) with at least one alpha nitrogen at the reactive silane end group according to fig. 1,

OMe o Fig. 1 OMe

H C — Si — CH C — Ov ^O Polymer v/\ O— C ^ \ H - Si— CH

3 I 2 \ / II ² I ³

N W

OMe _|-| ^u OMe preferably with two or more silane terminated end groups, preferably wherein the nitrogen forms part of a urethane bond, wherein Me is C¾, wherein the polymer is a polyether or a polyurethane or a combination thereof, wherein the polyether preferably is selected from branched or unbranched propylene glycol polyether, more preferably with less than 3 branches, (lb) 3-50 wt.% of at least one second silane-terminated polymer (STP) with at least one gamma nitrogen at the reactive silane end group according to fig. 2, and/or

(lc) 0.1-45 wt.% of at least one third silane-terminated polymer (STP) with no nitrogen close to the reactive silane end group, (Id) 0-5 wt.% of at least one fourth silane-terminated polymer (STP) with no nitrogen at the reactive silane end group according to fig. 3, in partic ular 0.1-3 wt.%,

OMe Fig. 3 Ϊ ² OMe

I H ₂ / \ I

H C— Si — CFI C—O v/\ Polymer 7O-C ^x E H - Si— CH

³ I ² / H ₂ ² I ³

OMe _|-| OMe wherein the polymer for figs. 2 and 3 is selected as above for fig. 1, (le) 5-60 wt.% of at least one filler, (If) 0-5 wt.% of at least one pigment or colorant, (lg) 0-5 wt.% of at least one rheology modifier, (lh) 0-50 wt.% of at least one first plasticizer, wherein the plasticizer is preferably selected from benzoates, phthalates, terephthalates, polyols, hydrated versions of phthalates, terephthalates, benzoates, and combinations thereof, (li) 0-5 wt.% of at least one adhesion promotor, (lj) 0-8 wt.% of at least one drying agent, (lk) 0-5 wt.% of at least one of an anti-oxidant, an UV-stabilizer, and a hindered amine light stabilizer, (11) 0.0 -2 wt.% of one or more of a fungicide, a bactericide, and an algaecide, (lm) 0 -5% of a catalyst, preferably chosen from organometal compounds, such as organotin, organo zinc, and organo bismuth compounds, and amines, (In) <0.2 wt.% free water, preferably <0.01 wt.%, more preferably <10 ⁴ wt.%, the second booster component, comprising (2a) 20-70 wt.% of at least one second plasticizer, preferably at least one polyol, having a molecular weight of 2000 - 25000 Da, having a functionality of two, three, or more, and a hydroxyl number of 5- 50 mgKOH/g, (2b) 20-60 wt.% of at least one of clay, CaCC , carbon black, silica, zeolite, talc, mica, kaolin, dolomite, aluminium trihydrate, and a calcium inosilicate mineral (Ca- Si03), such as wollastonite, preferably precipitated or grounded CaCC , which may be coated or not, and/or preferably a fumed silica, (2c) 0.01-5 wt.% of at least one surfactant, (2d) 0.0-10 wt.% of at least one silane terminated amine, such as 3-aminopropyl-trimethox- ysilane or 3 -aminopropyl-tri ethoxy silane, (2f) 3-60 wt.% water, wherein first and second component are provided in a volume ratio of 0.1 : 1 to 100:0, and wherein all weight percent ages are based on the respective first and second component. It has now unexpectedly been found that the use of the present more reactive polyether polymer in a 2C-system leads to the desired combination of properties by using a silane-terminated polymer (STP) with an alpha nitrogen at the reactive silane end group. This type of STP -polymer, for example sold under the trade name Geniosil, is found to be very reactive. This reactivity is considered due to the secondary alpha-amino group in the polymer chain. In praxis, in an alternative embodiment, a combination may be chosen between polymers with an alpha nitrogen, and a polymer with a gamma-nitrogen, or no nitrogen at all, to optimize the reactivity, and to balance the open time and cure speed. An additional advantage is there is no need for the use of a catalyst, such as a heavy metal catalyst, like a tin catalyst. Other ingredients such as fillers, stabi lizers, pigments, rheology modifiers, plasticizers, adhesion promotors, drying agents, antiox idants, UV-stabilizers, and biocides may be added in desired quantities. Also, a hardening catalyst, for example an amine could be present. The A-part (also referred to as first part or component) of the 2C-adhesive can therefore be able to cure without part B (also referred to as second part or component), using water from the air. In the 2C-system the second compo nent typically holds the water needed for the reaction. To obtain a mixture which is fully miscible with part A, this part consists, apart from water, of a plasticizer, such as a polyol, or a mixture of polyols, a filler, such as a fine calcium carbonate, preferably a precipitated cal cium carbonate, as to increase the viscosity, a fumed silica and one or more surfactants to homogenize the mixture. Additionally, a silane terminated amine such as 3 -aminopropyl-tri - m ethoxy silane or 3 -aminopropyl-tri ethoxy silane could be present. An example of a single 1C sealant of the prior art adhesive has an open time of ~42 minutes. It will reach a strength (F max) of ~2.8 MPa after 24 hours at RT, and 50%RH. Once boosted as described above the open time is not compromised and is still 37-43 min. However, the present F _max is already 1,4-1,65 MPa after two hours, and reaches 3,7-3,85 MPa after 24 hours, hence much higher. It has been found that the sealant of the present invention has improved self-healing proper ties. The hydroxyl value or hydroxyl number is defined as the number of milligrams of po tassium hydroxide required to neutralize acetic acid taken up on acetylation of one gram of a chemical substance that contains free hydroxyl groups, in this case the at least one second plasticizer. Hydroxyl value is a measure of the content of free hydroxyl groups in a chemical substance, usually expressed in units of the mass of potassium hydroxide (KOH) in milli grams equivalent to the hydroxyl content of one gram of the chemical substance (g KOH/g second plasticiser). The hydroxyl value can be calculated using the following equation. The acid value (AV) of the substance, determined in a separate experiment, enters into this equa tion as a correction factor in the calculation of the hydroxyl value (HV):

HV=[{ (56.1 )(N)(V _B -V _acet ) } /W _acet ]+AV} wherein HV is the hydroxyl value; VB is the amount (ml) potassium hydroxide solution re quired for the titration of the blank; V _aCet is the amount (ml) of potassium hydroxide solution required for the titration of the acetylated sample; W _aCet is the weight of sample (in grams) used for acetylation; N is the normality of the titrant; 56.1 is the molecular weight of potas sium hydroxide; AV is a separately determined acid value of the chemical substance. The content of free hydroxyl groups in a substance can also be determined by methods other than acetylation. ASTM D 1957 and ASTM E222-10 describe several versions of this method of determining hydroxyl value.

In a second aspect the present invention relates to a product comprising an adhe sive according to the invention, preferably wherein the product comprises large adhered parts, and/or is selected from vehicles, such as trucks, buses, and trains.

In a third aspect the present invention relates to a use of an adhesive composition according to the invention, for one or more of rapid hardening, long open time, such as >30 minutes, rapid strength built-up, such as F _max ^> 1 2 MPa after two hours, good elasticity, good strength, such as > 4.3 MPa after 24 hours (@590% elongation), good durability, good adhesion, free of tackiness, self-healing, water-tightness, a high bulk modulus after 24 hours, such as of > 1.2 MPa, and combinations thereof.

Thereby the present invention provides a solution to one or more of the above-men tioned problems.

Advantages of the present description are detailed throughout the description. DETAILED DESCRIPTION OF THE INVENTION

The present invention relates in a first aspect to an adhesive composition according to claim 1.

In an exemplary embodiment of the present adhesive in the first component the at least one first silane-terminated polymer (STP) is reactive.

In an exemplary embodiment of the present adhesive in the first component the at least one first silane-terminated polymer (STP) comprises <10 silane end groups with an al pha nitrogen, preferably 1-5 silane end groups with an alpha nitrogen, such as 2-4 silane end groups. In an exemplary embodiment the present adhesive in the first component com prises (la) 1-20 wt.% of the at least one first silane-terminated polymer, preferably 3-15 wt.%, more preferably 4-12 wt.%, such as 5-10 wt.%.

In an exemplary embodiment the present adhesive in the first component com prises (lb) 3-45 wt.% of at least one second silane-terminated polymer, preferably 12-40 wt.%, more preferably 20-35 wt.%, such as 25-30 wt.%.

In an exemplary embodiment the present adhesive in the first component com- prises(lc) 0.1-4 wt.% of at least one third silane-terminated polymer, preferably 0.2-2 wt.%, more preferably 0.3-1.5 wt.%, such as 0.5-1.1 wt.%.

In an exemplary embodiment of the present adhesive in the first component com prises (la,b,c) the silane-terminated polymer (STP) each individually comprise a polyether, wherein the polyether preferably is selected from branched or unbranched glycol polyethers, more preferably polypropylene glycol polyethers, such as with <3 side-branches (see e.g. fig.

4)·

In an exemplary embodiment of the present adhesive in the first component the polyether has an average molecular mass Mn of 400-4000 kDa (ISO 472).

In an exemplary embodiment of the present adhesive in the first component (la,b,c) the silane-terminated polymer (STP) each individually comprise a carboxyl moiety between the polymer and silane group, wherein the carboxyl moiety preferably comprises 1- 3 carbons.

In an exemplary embodiment of the present adhesive in the first component the additives are selected from catalysts, co-catalysts, rheology control agents, pigments, pig ment pastes, HALS, UV stabilizers, antioxidants, adhesion promotors, and drying agents.

In an exemplary embodiment of the present adhesive in the first component the adhesion promotor is selected from Amino-propyl-tri-ethoxy-silane (APTES) and Amino- propyl-tri-methoxy-silane (APTMS).

In an exemplary embodiment of the present adhesive in the first component the rheology modifier is selected from fumed silica, carbon black, and polyamide waxes.

In an exemplary embodiment the present adhesive in the first component com prises (le) 15-55 wt.% of at least one filler, preferably 30-50 wt.%, more preferably 40-45 wt.%

In an exemplary embodiment the present adhesive in the first component com prises in the first component (In) 0-5 wt.% hardening catalyst, such as an amine, and (lo) 0- 5 wt.% of at least one further additive.

In an exemplary embodiment of the present adhesive in the first component the filler is selected from chalk, precipitated chalk, grounded chalk, coated precipitated chalk, coated grounded chalk, silica, alumina, carbon black, and combinations thereof.

In an exemplary embodiment the present adhesive in the second component com prises (2a) 30-60 wt.% of at least one second plasticizer, preferably 40-50 wt.%. In an exemplary embodiment the present adhesive in the second component com prises (2b) 30-50 wt.% at least one inorganic material selected from clay, CaC0 ₃ , carbon black, silica, zeolite, talc, mica, kaolin, dolomite, aluminium trihydrate, and a calcium inosil- icate mineral (CaSi03), such as wollastonite, preferably 4-7 wt.%, preferably precipitated CaC0 _3.

In an exemplary embodiment of the present adhesive in the second component (2b) the inorganic material has an average particle size of 0.01-300 pm, preferably 0.02-10 pm, more preferably 0.05-1 pm, such as 0.07-0.2 pm.

In an exemplary embodiment the present adhesive in the second component com prises (2b) 0.2-10 wt.% at least one silica, preferably a fumed silica, preferably 1-4 wt.%, and/or

In an exemplary embodiment the present adhesive in the second component com prises (2c) 0.05-2 wt.% of at least one surfactant, preferably 0.1-1.5 wt.%„ and/or

In an exemplary embodiment the present adhesive in the second component com prises (2d) 0.5-8 wt.% of at least one silane terminated amine, preferably 2-6 wt.%, such as 4-5 wt.%.

In an exemplary embodiment the present adhesive in the second component com prises (2e) 0.1 -1.7 wt.% of one or more of a fungicide, a bactericide, and an algaecide, pref erably 0.3-1.5 wt.%, such as 0.5-1.4 wt.%.

In an exemplary embodiment of the present adhesive with the proviso that no heavy metal catalyst is present.

In an exemplary embodiment the present adhesive comprises in the second compo nent (2g) 0-60 wt.% of at least one second plasticizer, preferably 5-45 wt.%, such as 35-45 wt.%, and optionally, and (2i) 0-10 wt.% of an accelerator, preferably 1-8 wt.%, such as 3-6 wt.%.

In an exemplary embodiment of the present adhesive the at least one first and at least one second plasticizer each individually are selected from benzoic acid esters, phthalic acid diesters, terephthalic acid diesters, benzoates, phthalates, terephthalates, polyols, hydro genated versions of phthalates, terephthalates and benzoates, and combinations thereof.

In an exemplary embodiment of the present adhesive the first and second compo nent are provided in a weight ratio of 40:1 to 0.5:1, preferably 30:1 to 0.6:1, more preferably 25:1 to 0.7:1, such as 20:1 to 2:1.

In an example of the present adhesive it may comprise a combination of the above.

In an exemplary embodiment the present use is in one-sided or two-sided bonding, especially of bonding of large surfaces of 0.5-30 m ² , such as 0.5-15 m ² .

In an exemplary embodiment the present use is for adhering a workpiece, such as a car window, and a car panel.

The invention is further detailed by the accompanying figures and examples, which are exemplary and explanatory of nature and are not limiting the scope of the invention. To the person skilled in the art it may be clear that many variants, being ob vious or not, may be conceivable falling within the scope of protection, defined by the present claims.

FIGURES

Figure 1 : A first silane-terminated (Si(ORi)2R3) polymer (STP) with at least one alpha nitrogen at the reactive silane end group according to the invention.

Figure 2 shows a second silane-terminated polymer (STP) with at least one gamma nitrogen at the reactive silane end group.

Figure 3 shows a third silane-terminated polymer (STP) with no nitrogen close to the reactive silane end group.

Fig. 4 shows a propylene glycol moiety.

EXAMPLES/EXPERIMENTS

The invention although described in detailed explanatory context may be best un derstood in conjunction with the accompanying examples.

Table 1 and table 2 show a list of sealants and boosters according to the invention. There are 6 sealants (SO [prior art] and S1-S5, according to the invention) tested with an open time around 20 minutes. In table 3 the results of open time, curing time and Fmax are presented for these sealants combined with one of the boosters of table 2. The sealant with the fastest strengthening is sealant 3, which contains the alpha N polymer of the present in vention. Moreover, sealant 3 is still the fastest when the open time is extended from 20 till 30 minutes by choosing a different booster. When only a minor amount of gamma N poly mer is added, such as in sealant 1, the curing speed is already halved compared to sealant 3, but still considerably faster than the prior art. Additionally, the sealant containing gamma O polymer (sealant 0) needs about 25 hours to reach half of the strength which the sealant with the alpha N polymer (sealant 3) reaches in 3 hours.

Table 4 shows the open time and curing speeds, combined with the final properties of the sealants after one week (168 h) of curing. It is clear that sealant 3 has the highest curing speed, for both boosted and non-boosted sealant, after 1 day and 1 week of curing because sealant 3 has the highest FI 00 value. Moreover, the sealant has the highest curing speed, re gardless of the type of booster. Additionally, it is especially remarkable that sealant 3 is free of (tin-) catalyst.

Additionally the formula SO and S3 were tested without booster according to EN ISO 1465, RVS 2mm layer of adhesive, 12,5 mm x 25 mm overlap. Cure was performed at low temperature and humidity, 10°C and 30%RH, so the cure was far from complete. For for mula SO a F _max was found of 0,38 N/mm2 but for formula S3 this was 0,82 N/mm2 , thus showing the increased speed of adhesive strength build-up of the present invention.

Finally dumbbells were prepared without booster and tested according to DIN 53504, dumb bell type 2, but measured after 1 day at 10°C and 30%RH. The results in table 5 clearly demonstrate the increased cure rate or strength build-up.. Formulation of sealants Table 1:

Gamma O: polymer with the silyl group on the gamma position from the oxygen (prior art); Alpha N: polymer with the silyl group on the alpha position from the nitrogen (component la); Gamma N: polymer with the silyl group on the gamma position from the nitrogen (com ponent lb)

Formulation of boosters table2:

Results table 3: open time, curing time, Fmax

Results table 4: open time and curing speeds Results table 5: Fmax of Dumbbells after DIN 53504 after 1 day cure at 10°C and 30%RH

Test Methods

Open time and curing time

Open time and curing time were determined by using a Beck Roller recorder, usually known as BK-recorder such as sup-plied by for example TQC-sheen.

With use of a film applicator an adhesive film of 450pm is applied to a glass plate. The B.K Drying recorder pulls a needle through the adhesive film at a set speed correlating with time.

After the test different stages are observed. By measuring the start and end of the dif- ferent stages open time and curing time can be calculated.

Using a 450pm film applicator a film of fresh adhesive is applied on to a degreased glass plate (25 x 300 mm). Immediately after application the glass plate is inserted in the BK-recorder, the needle is placed on the adhesive, and if desired BK-recorder weights may be applied to increase needle pressure to be able to scratch through the adhesive, and the re- corder is started. After the needle has reached the end of the line the open time and the cure time can be calculated from the distance the needle has passed scratching through the adhe sive onto the glass plate (open time) and scratching through the adhesive to the glass plate added with the distance scratching through the adhesive, but no longer through to the glass plate (curing time), respectively. This method is an adaptation of ASTM D5895, EN 14022, and ISO 9117-4.

Force at 100% elongation (F100), maximum force (Fmax) and elongation at break (EAB) were determined conform DIN 53504 using a dumbbell type 2 (Schulterstab S2).