BINDER COMPOSITIONS AND USES THEREOF

Abstract

The present invention relates to new aqueous curable binder compositions comprising a carbohydrate compound, a first cross linker and a second cross linker different from the first capable of undergoing radical polymerization and possibly a free radical initiator.

Claims

1.-18. (canceled)

19. A method for the preparation of a bonded assembly of fibrous materials or particulate or sheet materials comprising (i) the provision of (a) a carbohydrate compound, (b) a first cross-linker and (c) a second cross-linker capable of undergoing radical polymerization and optionally (d) a free radical initiator, and/or of reaction product of (a) and (b) and/or (c), (ii) the successive or simultaneous application of (a), (b), and (c) and optionally (d), optionally as an aqueous composition comprising reaction product of (a) and (b) and/or (c), onto fibrous or cellulosic particulate or sheet material to produce resinated material, and (iii) subjecting the resulting resinated material to conditions for radical polymerization of (a) and (c) and to curing conditions thereby allowing for evaporation of excess water wherein the first cross-linker is selected from monomeric polycarboxylic acids, and wherein the second cross linker capable of undergoing radical polymerization is selected from acrylamides and methacrylamides, acrylates and methacrylates, acrylic acids and their salts, acrylonitrile, carbohydrate monomers, maleimide, and mixtures thereof.

20. The method of claim 19 characterized by one or more of the following features wherein the cross-linking of the carbohydrate compound with the first and/or the second cross-linker is effected at a temperature ranging from ambient temperature (e.g. 20? C.) to 100? C., during a required period of time to generate the desired cross-linked material, wherein curing is effected at a temperature ranging from 90-200? C.

21. (canceled)

22. The method of claim 19 wherein, after polymerization, the reaction product is subjected to UV or IR radiation.

23. A product comprising an assembly of fibrous material or cellulosic particulate or sheet material bonded with an aqueous curable binder composition comprising a carbohydrate compound, a first cross-linker selected from a carboxyl function bearing compound which forms esters with the carbohydrate compound, and a second cross-linker, the second cross-linker being different from the first and being capable of undergoing radical polymerization, and optionally a free radical initiator; wherein the carboxyl function bearing compound is selected from a monomeric polycarboxylic acid, and wherein the second cross-linker capable of undergoing radical polymerization is selected from an acrylamide monomer and a methacrylamide monomer, an acrylate monomer and a methacrylate monomer, an acrylic acid and its salts, acrylonitrile, a carbohydrate monomer, maleimide, and mixtures thereof.

24. The product of claim 23 comprising an assembly of fibrous material and being an insulation product.

25. The product of claim 23 comprising an assembly of cellulosic particulate or sheet material, and being a wood fiber board, wood particle board, or plywood.

Description

[0057] The invention will be explained in more details in the examples below with reference to the attached Figures, in which:

[0058] FIGS. 1 and 2 show the kinetic evaluation of curing determined at 160? C. for binder formulations of 65% T&L Stadex79+20% malic acid+5% SHP+10% second cross linker (DMAEMA, DEGDMA or HEMA)+1% 1,1-azobis(cyclohexanecarbonitrile) radical initiator, by determination of bond strength and stiffness at different cure times.

MATERIALS FOR BINDER FORMULATION

[0059] Different grades of starch polymers such as Stadex? 79, Stadex? 125, Stadex?201 Waxy, Ethylex? 2005S Gum, Ethylex? 2040 Gum and Ethylex? 2095 Gum were purchased from Tate & Lyle. Acrylate monomers such as poly(ethylene glycol) diacrylate, hexanediol diacrylate, ethylene glycol dimethacrylate, and di(ethylene glycol)dimethacrylate and other acrylate monomers such as hydroxyethyl methacrylate (HEMA), dimethylaminoethyl methacrylate (DMAEMA), hydroxy ethyl acrylate (HEA) were purchased from Aldrich. Malic acid (MA), glutamic acid and radical initiators such as 4,4-Azobis-4-cyanopentanoic acid (ABCPA), 1,1-Azobis (cyclohexanecarbonitrile) (ABCN) and Benzyl Peroxide (BPO) were also purchased from Aldrich.

Preparation of Binder Compositions

[0060] First, a desired amount of starch was dissolved in water and stirred constantly for 45 minutes at room temperature. If required, temperature may be raised up to 80? C. in order to dissolve the starch in water. For crosslinking reaction, various concentrations (10-30%) of malic acid and glutamic acid were added individually to the starch solution, followed by the addition of the required amount of SHP (0.5-5%), depending on the formulation. The obtained solution was stirred continuously for 45 minutes in the temperature range of 70-90? C. in order to allow for crosslinking.

[0061] In a second step, diacrylate or acrylate or polyacrylate monomers were added together with radical initiator and the resulting mixture was stirred continuously at a pre-set temperature in order to form a complex polymer network. The Energy required for radical initialisation may be adduced by increase of temperature. Other means are available too, like IR, RF or UV radiation.

[0062] The crosslinking of starch can take place between various molecules such as amylose to amylose, amylose to amylopectine or amylopectin to amylopectin. when the ester linkage is formed, a further crosslinking may be carried out with polyacrylates or acrylate monomers, making use of radical initiator.

[0063] The obtained aqueous composition was applied to a glass veil which was then subjected to curing. Samples were prepared from the cured veil and subjected to different tests as described below.

Determination of Binder Weight Loss

[0064] Aqueous binder compositions (solutions) as prepared above were brought to a solid content of 22.5%. About 12 g of solution was placed into aluminium petri dish, which was kept in an oven at 140? C. for 2 hours. Theoretical and experimental solid was measured and solid loss calculated.

Kinetic Evaluation of Curing

[0065] Glass microfiber (Whatman?) GF/A filters were impregnated with binder solution as prepared above prior to curing at various time points at a set temperature. Samples were kept on the top shelf in the oven to avoid high moisture content inside the oven during curing. For each binder solution, samples were cured from 3 minutes to 20 minutes. After curing, each cured sample was cut into an appropriate size with a length (150 mm) and width (20 mm), and then mechanical testing was performed for stiffness (elastic modulus) and bond strength analysis. Results of the kinetic study or cure rate study are presented in FIGS. 1 and 2.

[0066] It appears that the binder compositions cure within a time period ranging from 3-5 minutes.

Bond Strength Analysis Using the Veil Method

[0067] Commercial PF (phenol formaldehyde) impregnated (A4 size) glass fiber veils were placed into a muffle furnace oven for 30 minutes at 600? C. in order to burnout the PF binder, and were then allowed to cool for 30 minutes. The obtained veil samples were weighted.

[0068] Approx. 400 g binder solution samples were poured into dip trays, and the obtained veil samples carefully fully immersed into the relevant binder solutions. The impregnated veils were cured at desired temperature for desired periods of time. Binder content was then measured and bond strength determined as follows.

[0069] The bond strength of the relevant cured binder impregnated veils was determined by means of a mechanical testing instrument (M350-10CT). For each test a cured binder impregnated A4 veil was cut into 8 equal strips. Each strip was tested separately using a 50 Kg load cell (DBBMTCL-50 kg) at an automated test speed of 10 mm/min controlled by winTest Analysis software. Glass veil tensile plates were attached to the testometric machine in order to ensure a 100 mm gap between plates. Samples were placed vertically in the grippers; and the force was tarred to zero. Various parameters such as maximum load at peak, stress at peak and modulus at peak were evaluated by the software, and data presented as an average of 8 samples with standard deviation. The average maximum load at peak or stress at peak defined as the bond strength.

Evaluation of Weathering Stability

[0070] An electronically controlled autoclave system (a steam pressure vessel) was used to sterilise the cured binder veils samples for subsequent strength testing. Cured binder impregnated veils were placed in an autoclave (J8341, Vessel: PVO2626 with associated safety valve, door interlock and integrated pipework) system. Samples were treated at 90% humidity and at a temperature ranging from 40? C. to 110? C. (full cycle), at a pressure of up to 2.62 bar, for 3 hours. The samples were dried completely in order to ensure no moisture remains onto the veils. The autoclave treated samples were tested for bond strength by means of testometric machine (M350-10CT) described here above, and the results were compared with those of untreated samples.

Example 1

[0071] Determination of binder solid weight loss upon curing at 140? C. for 2 hours, as presented in Table 1. Aqueous binder compositions (solutions) as prepared above were brought to a solid content of 22.5%. About 12 g of solution was placed into aluminium petri dish, which was kept in an oven at 140? C. for 2 hours. Theoretical and experimental solid was measured and solid loss calculated. The binder compositions comprise starch as a polysaccharide, malic acid (MA) as a cross linker, SHP, acrylates (HEMA, DEGDMA, HEA or MAA) as cross linker capable of undergoing radical polymerization, and ABCN as a radical initiator.

TABLE-US-00001 TABLE 1 Binder Materials Composition Solid Loss (%) Stadex79/MA/SHP/HEMA/ABCN 70/15/5/10/1 1.76 Stadex79/MA/SHP/HEMA/ABCN 60/25/5/10/1 3.16 Stadex79/MA/SHP/DEGDMA/ABCN 60/25/5/10/1 4.46 Stadex79/MA/SHP/DEGDMA/ABCN 70/15/5/10/1 2.69 Stadex79/MA/SHP/HEA/ABCN 60/25/5/10/1 2.34 Stadex79/MA/SHP/MAA/ABCN 60/25/5/10/1 7.61 Stadex79/CAMH/SHP/HEMA 75/15/5/10 1.2 Stadex79/CAMH/SHP/HEMA/ABCN 75/15/5/10/1 1.0 Stadex79/CAMH/SHP/HEMA 70/20/5/10 0.8 Stadex79/CAMH/SHP/HEMA/ABCN 70/20/5/10/1 0.7 Stadex 79: Starch CAMH: Citric acid monohydrate SHP: sodium hypophosphite HEMA: 2-hydroxyethyl methacrylate DEGDMA: di(ethylene glycol)dimethacrylate HEA: hydroxyethyl acrylate MAA: methacrylic acid ABCN: 1,1 Azobis(cyclohexanecarbonitrile)

Example 2

[0072] The kinetic evaluation of curing determined at 160? C. for binder formulations of 65% T&L Stadex79+20% malic acid+5% SHP+10% cross linker (DMAEMA, DEGDMA or HEMA)+1% 1,1-azobis(cyclohexanecarbonitrile) radical initiator, as presented in FIG. 1, with a standard deviation of five replicates. The binder solution composition was prepared and the bond strength of corresponding sample was measured according to the procedure described in the previous section.

Example 3

[0073] The kinetic evaluation of curing determined at 160? C. for binder formulations of 65% Stadex79+20% malic acid+5% SHP+10% crosslinker (DMAEMA, DEGDMA or HEMA)+1% 1,1-azobis(cyclohexanecarbonitrile) radical initiator, as presented in FIG. 2, with a standard deviation of five replicates. The binder solution composition was prepared according to the description given in the previous section. The stiffness (i.e. the modulus of elasticity) of corresponding samples is measured and plotted as a function of cure time (FIG. 2).

Example 4

[0074] Bond strength analysis of three different binder formulations is presented. (i) Formulation one comprising starch (stadex 79), polyacid (citric acid monohydrate (CAMH)) as a first crosslinker and sodium hypophosphite (SHP); (ii) the second formulation comprises additionally a second cross linker 2-hydroxyethyl methacrylate (HEMA) in formulation (i) and the third formulation comprises ABCN as a radical initiator plus the second cross linker of the second formulation. Here, the bond strength is defined as the maximum load at which the veil impregnated cured samples breaks down. Results also show with corresponding binder material formulations and ratios of unweathered and weather treated veil samples. These impregnated veils were cured in two steps comprising curing at 90? C. for 5 minutes then at 180? C. for 10 minutes. The mechanical tests were performed at dry conditions for both unweathered and weather treated veil samples, and the results are presented with standard deviation of eight replicates, as shown in Table 2. Results show the bond strength of second and third formulations are significantly higher as compared to the first formulation for both unweathered and weather treated samples.

TABLE-US-00002 TABLE 2 Unweathered Weather treated Veil Samples Veil Samples Bond Bond Strength STDEV Strength STDEV Formulations (N) (+/?) (N) (+/?) Stadex79/CAMH/SHP: 81.9 9.03 49.31 7.48 80/20/5 Stadex79/CAMH/SHP/HEMA: 94.85 8.83 46.87 3.73 70/20/5/10 Stadex79/CAMH/SHP/HEMA/ 100.65 5.78 56.76 5.04 ABCN: 70/20/5/10/1

Example 5

[0075] Bond strength analysis of various binder formulations of monosaccharide (e.g. Dextrose monohydrate, DMH), disaccharide (Maltose monohydrate, Maltose MH) and polysaccharide (from 3 to 19 saccharide units), and their combination with starch (Stadex 79), CAMH, HEMA and AEON with or without SHP is presented. The mechanical tests were performed on unweathered cured (180? C. for 15 minutes) veil samples at dry conditions, and the results are presented with standard deviation based on eight replicates, as shown in Table 3.

TABLE-US-00003 TABLE 3 Average Bond Strength STDEV Formulations (N) (+/?) DMH/CAMH/HEMA/ABCN: 70/20/10/1 74.22 11.23 DMH/CAMH/HEMA/SHP/ABCN: 70/20/10/5/1 74.75 10.19 MaltoseMH/CAMH/HEMA/ABCN: 70/20/10/1 58.16 5.22 MaltoseMH/CAMH/HEMA/SHP/ABCN: 60.37 8.62 70/20/10/5/1 Maltodextrin/CAMH/HEMA/ABCN: 70/20/10/1 73.85 5.56 Maltodextrin/CAMH/HEMA/SHP/ABCN: 85.33 8.13 70/20/10/5/1 Stadex 79/DMH/CAMH/HEMA/ABCN: 63.50 9.42 50/20//20/10/1 Stadex 79/DMH/CAMH/HEMA/SHP/ABCN: 85.20 4.08 50/20//20/10/5/1 Stadex 79/MaltoseMH/CAMH/HEMA/ABCN: 57.04 6.73 50/20//20/10/1 Stadex 79/MaltoseMH/CAMH/HEMA/SHP/ABCN: 86.76 9.37 50/20//20/10/5/1 Stadex 79/Maltodextrin/CAMH/HEMA/ABCN: 55.98 6.37 50/20//20/10/1 Stadex 79/Maltodextrin/CAMH/HEMA/SHP/ 95.92 12.37 ABCN: 50/20//20/10/5/1

Example 6

[0076] Further bond strength analysis of various binder formulations of different polysaccharides/starches with CAMH, HEMA and AEON with SHP is presented. The mechanical tests were performed on weathered cured (190? C. for 10 minutes) veil samples, under dry conditions, as per Example 4 (except that the curing temperature was 190? C. instead of 180? C. and that the curing time was 10 minutes instead of 15 minutes). The results are presented in Table 4 and Table 5 with standard deviation based on eight replicates.

TABLE-US-00004 TABLE 4 Unweathered Weathered Veil samples Veil samples Bond Bond strength STDV strength STDV Formulations (N) (+/?) (N) (+/?) Stadex125/CAMH/SHP: 94.92 11.26 51.53 5.27 80/20/5 Stadex125/CAMH/SHP: 93.01 7.88 50.84 8.89 70/30/5 Stadex125/CAMH/SHP/HEMA/ 92.19 9.43 53.93 6.93 ABCN: 70/20/5/10/1 Stadex201/CAMH/SHP: 87.38 9.05 56.19 2.84 80/20/5 Stadex201/CAMH/SHP: 92.06 9.00 49.71 6.31 70/30/5 Stadex201/CAMH/SHP/HEMA/ 89.64 9.32 55.57 7.02 ABCN: 70/20/5/10/1

TABLE-US-00005 TABLE 5 Unweathered Weathered Veil samples Veil samples Bond Bond strength STDV strength STDV Formulations (N) (+/?) (N) (+/?) StEthylex2005S/CAMH/SHP: 98.16 8.47 73.49 4.35 80/20/5 StEthylex2005S/CAMH/SHP: 96.79 9.56 64.2 8.77 70/30/5 Ethylex/CAMH/SHP/HEMA/ 87.25 6.25 57.65 10.08 ABCN: 70/20/5/10/1 StEthylex2040/CAMH/SHP: 116.51 5.33 86.33 7.64 80/20/5 StEthylex2040/CAMH/SHP: 116.01 4.49 70.29 6.38 70/30/5 Ethylex/CAMH/SHP/HEMA/ 100.05 9.58 73.23 6.90 ABCN: 70/20/5/10/1 StEthylex2095/CAMH/SHP: 113.46 17.07 91.07 6.40 80/20/5 StEthylex2095/CAMH/SHP: 103.98 9.96 85.40 6.30 70/30/5 Ethylex/CAMH/SHP/HEMA/ 111.95 6.24 66.06 6.50 ABCN: 70/20/5/10/1

[0077] The above examples make use of commercially available starches as mentioned above. As shown below by way of viscosity measurements, Stadex starches are low molecular weight starches, Ethylex 2040 and 2095 starch are higher molecular weight starches.

TABLE-US-00006 TABLE 6 Viscosity measurement of modified starches. Viscosity was measured using DV-II + Pro Viscometer Brookfield LV. All measurements were done at a constant temperature. Concen- Viscosity Sample tration Temp. Value Name (wt. %) (? C.) (cps) Comments Stadex 79 20 35 6.67 Stadex 125 20 35 8.40 Stadex 201 20 35 4.17 Starch Ethylex 15 35 67 2005S Starch Ethylex 20 35 275 2005S Starch Ethylex 20 35 xxx The viscosity above 2040 the highest detection limit of the machine. Starch Ethylex 15 35 9900 Highly viscose. 2040 Starch Ethylex 20 35 xxx The viscosity above 2095 the highest detection limit of the machine. Starch Ethylex 15 35 xxx The viscosity above 2095 the highest detection limit of the machine. Starch Ethylex 10 70 >101,000 Highly viscose (below 2095 70? C. machine did not detect).