阅读说明：本技术 用于基于乳酸的热熔胶的增粘剂 (Tackifier for lactic acid-based hot melt adhesive ) 是由 K·B·布拉姆 C·F·H·舍克斯 R·J·范斯特里恩 R·J·A·史蒂文斯 于 2019-12-18 设计创作，主要内容包括：本发明涉及基于乳酸的具有无定形乳酸低聚物增粘剂的热熔胶。特别地,热熔胶(HMA)包含：乳酸和己内酯共聚物树脂、结晶乳酸低聚物蜡和所述无定形乳酸低聚物增粘剂,其特征在于,无定形乳酸低聚物增粘剂包含a)乳酸单体与b)含有三个或更多个羟基和/或氨基的多官能聚合引发剂的无定形聚合产物。本发明还涉及无定形乳酸低聚物增粘剂在基于乳酸的热熔胶中的用途、使用包含所述无定形乳酸低聚物增粘剂的热熔胶将基板粘合在一起的方法以及特定的无定形乳酸低聚物增粘剂及其制备方法。(The invention relates to a lactic acid-based hot melt adhesive with amorphous lactic acid oligomer tackifier. In particular, the Hot Melt Adhesive (HMA) comprises: lactic acid and caprolactone copolymer resins, crystalline lactic acid oligomer waxes and the amorphous lactic acid oligomer tackifiers, characterized in that an amorphous lactic acid oligomer tackifier comprises an amorphous polymerization product of a) a lactic acid monomer and b) a polyfunctional polymerization initiator containing three or more hydroxyl groups and/or amino groups. The invention also relates to the use of amorphous lactic acid oligomer tackifiers in lactic acid-based hot melt adhesives, methods of bonding substrates together using hot melt adhesives comprising the amorphous lactic acid oligomer tackifiers, and specific amorphous lactic acid oligomer tackifiers and methods of making the same.)

1. A Hot Melt Adhesive (HMA) comprising:

-a lactic acid and caprolactone copolymer resin,

-crystalline lactic acid oligomer wax, and

-an amorphous lactic acid oligomer tackifier,

characterized in that the amorphous lactic acid oligomeric tackifier has a crystallinity defined by its melting enthalpy of at most 2.5J/g and comprises a) a lactic acid monomer and b) a monomer containing three or more hydroxyl groups andamorphous polymerization product of polyfunctional polymerization initiator of amino group, wherein the amorphous polymerization product of amorphous lactic acid oligomer tackifier has number average molecular weight (M)_n) 1000 to 10000 g/mol.

2. The hot melt adhesive according to claim 1, wherein the polyfunctional polymerization initiator of the amorphous lactic acid oligomer tackifier contains three or more hydroxyl groups, particularly four or more, more particularly five or more, even more particularly six or more hydroxyl groups.

3. The hot melt adhesive of claim 1 or 2, wherein the amorphous polymeric product of the amorphous lactic acid oligomeric tackifier has a number average molecular weight (M)_n) Is 2000-4000g/mol, especially 2500-3500 g/mol.

4. The hot melt adhesive according to claim 2 or 3, wherein the polyfunctional polymerization initiator of the amorphous lactic acid oligomer tackifier is selected from the group consisting of D-sorbitol, pentaerythritol and dipentaerythritol, in particular D-sorbitol.

5. The hot melt adhesive according to any one of the preceding claims, wherein the lactic acid monomer of the amorphous lactic acid oligomer tackifier is derived from one or more of L-lactic acid, D-lactic acid, L-lactide, D-lactide and meso-lactide, in particular from L-lactic acid and/or L-lactide.

6. The hot melt adhesive according to any one of the preceding claims, wherein the ratio of lactic acid monomer per hydroxyl or amino group of the polyfunctional polymerization initiator in the amorphous polymerization product is from 2 to 25, in particular from 4 to 15, more in particular from 6 to 10 moles of lactic acid per mole of hydroxyl or amino groups.

7. The hot melt adhesive according to any one of the preceding claims, comprising from 30 to 80 wt% of copolymer resin, from 0.5 to 30 wt% of oligomeric wax and from 5 to 45 wt% of amorphous tackifier, in particular from 10 to 35 wt%, and more in particular from 15 to 25 wt%, based on the total weight of the hot melt adhesive.

8. The hot melt adhesive according to any one of the preceding claims, further comprising one or more additional components selected from nucleating agents, antioxidants, and stabilizers.

9. The hot melt adhesive of any one of the preceding claims, wherein the copolymer resin is a block copolymer comprising a first block and a second block, wherein

-the first block is an amorphous copolymer of lactic acid and caprolactone; and

the second block is a crystalline polymer of lactic acid.

10. Amorphous polylactic acid tackifier for a Hot Melt Adhesive (HMA) according to claims 2-9, comprising an amorphous polymerization product of a) lactic acid monomers and b) a polyfunctional polymerization initiator containing four or more hydroxyl groups, wherein the amorphous polymerization product has a number average molecular weight (M) of 1000 to 10000g/mol_n) Wherein the amorphous polylactic acid tackifier has a crystallinity defined by its melting enthalpy of at most 2.5J/g and a glass transition temperature of at least 30 ℃.

11. Process for the preparation of an amorphous polylactic acid tackifier according to claim 10, comprising the step of reacting a) lactic acid and/or lactide with b) a polyfunctional polymerization initiator containing four or more hydroxyl groups until a number average molecular weight (M) is obtained_n) 1000 to 10000g/mol of polymerization product to form an amorphous polymerization product.

12. Use of an amorphous polylactic acid tackifier in a hot melt adhesive, wherein the hot melt adhesive comprises a lactic acid and caprolactone copolymer resin and a crystalline lactic acid oligomer wax, wherein the tackifier and the hot melt adhesive are as defined in any one of claims 1 to 10.

13. A method for arranging substrates in fixed positions relative to each other, comprising the steps of: applying an amount of the hot melt adhesive of claims 1-9 in liquid form to a surface of a first substrate, applying a surface of a second substrate to the amount of the hot melt adhesive composition, and cooling the assembly of substrates and hot melt adhesive composition to a temperature below the melting point of the hot melt adhesive composition.

14. A method for arranging base panels in a fixed position relative to each other according to claim 13, wherein the base panels are elements of a carton.

Examples

Preparation of adhesion promoters

All oligomeric or polymeric tackifiers were prepared from the monomers shown in each of the following examples, using a 1L scale four neck glass setup reactor with agitation from an overhead stirrer, stannous (II) ethyl hexanoate as catalyst,126 as antioxidants and monomeric carbodiimidesAs a stabilizer. The polymerization is carried out at 180 ℃ and is stopped after a reaction time of at most 3 hours, at which point the target molecular weight (M) is reached_n)。

Number average molecular weight (M) by gel permeation chromatography_n) Liquid chromatography with a C18 column (which distinguishes molecular weights) was used, chloroform as solvent and run phase, polystyrene as reference and detection by refractive index.

Example 1: sorbitol and lactic acid oligomers derived from 100 wt% of L-lactide, M_nIt was 3000 g/mol.

751.4g of L-lactide (from Corbion) were reacted in the presence of stannous (II) ethyl hexanoate according to the general procedure described aboveB3) Was polymerized with 48.6g of D-sorbitol (from Sigma-Aldrich). M of the resulting lactic acid oligomer_n3000g/mol, a crystallinity of 0.5J/g or less, and a Tg of 40.3 ℃.

Example 2: sorbitol and lactic acid oligomers, derivativesFrom 88% by weight of L-lactide and 12% by weight of D-lactide, M_nIs 5000g/mol

678.4g of L-lactide (from Corbion) were reacted in the presence of stannous (II) ethyl hexanoate according to the general procedure described aboveB3) Polymerized with 92.5g of D-lactide (from Sigma-Aldrich). M of the resulting lactic acid oligomer_n5000g/mol, a crystallinity of 0.5J/g or less, and a Tg of 38.2 ℃.

Example 3: melamine and lactic acid oligomers derived from L-lactide, M_nIt was 3000 g/mol.

719.1g of L-lactide (from Corbion) were reacted in the presence of stannous (II) ethyl hexanoate according to the general procedure described aboveB3) With 31.8g of melamine (from Alfa Aesar). M of the resulting lactic acid oligomer_n3000g/mol, a crystallinity of 0.5J/g or less, and a Tg of 45.4 ℃.

Comparative example 1: neopentyl glycol and lactic acid oligomer derived from 88 wt% L-lactide and 12 wt% D-lactide, M_nIt was 5000 g/mol.

646.3g of L-lactide (from Corbion) were reacted in the presence of stannous (II) ethyl hexanoate according to the general procedure described aboveB3) And 88.1g of D-lactide (from Corbion)D) Polymerization with 15.6g of neopentyl glycol (from Perstorp AB). M of the resulting lactic acid oligomer_n5000g/mol, crystallinity lower than 0.5J/g, Tg 36.0 ℃.

Preparation of Hot melt adhesive formulations

Hot Melt Adhesives (HMA) were prepared using the different tackifiers prepared in examples 1-3 and comparative example 1 as detailed in table 1. Furthermore, preferably no gain is presentReference formulation of the adhesive, and use of a commercially available resin including rosin (e.g. Permalyn from Eastman)^TM5110 and pinclean from Lawter^TM2498E) And hydrocarbon resins (Eastotac from Eastman)^TMH-130W、Picco^TMA-100、Kristalex^TMF-100 and Regalite^TMTackifier of R1100CG) to prepare HMA formulations. However, these were not successfully prepared in view of the incompatibility of the tackifier with the copolymer resin and the oligomer wax and were therefore not further evaluated.

The hot melt formulations each contained 48.5 wt% copolymer resin, 18.5 wt% oligomeric wax, 3 wt% nucleating agent, and 30 wt% tackifier. The reference formulation without tackifier contained 48.5 wt% of the oligomeric wax (instead of 18.5 wt% of the oligomeric wax and 30 wt% of the tackifier). The copolymer resin was M with 15000g/mol prepared according to example 1 of WO2017/149019_nAnd a lactic acid caprolactone block copolymer of lactic acid/caprolactone ratio of 78/22.

The oligomeric wax is prepared by reacting L-lactide(s) (as described above for the tackifierB3, enantiomeric purity greater than 99%) with an M of 2250g/mol_nAnd a crystallinity of greater than 25J/g.

The nucleating agent is prepared by reacting D-lactide (A), (B), (C) and C) a) and C) a)D, enantiomeric purity greater than 99%) of a crystalline lactic acid oligomer having an M of 3500g/mol_nAnd a crystallinity of greater than 25J/g.

HMA formulations were prepared in glass flasks with overhead stirrer, where the adhesion promoter was melted at a temperature of 163 ℃ with stirring, the nucleating agent was added to the melted adhesion promoter and mixed until melted and a homogeneous mixture was obtained. The oligomer wax was added and mixed until molten and a homogeneous mixture was obtained. Finally, the copolymer resin was added in small portions and mixed until molten and a homogeneous mixture was obtained. The mixture was kept at 163 ℃ with stirring until application.

Physical characterization of HMA formulations

HMA formulations were evaluated by DSC and rheometer measurements.

DSC was determined as follows: using a hot-cold-hot cycle starting from-50 ℃, heat was applied at a rate of 10 ℃/min to 220 ℃, then cooled at the same rate and the first heating step was repeated.

The complex viscosity of the HMA formulation was determined using a TA Instrument dynamic mixing rheometer 2, using an angular frequency of 10rad/s and a strain of 10% at 163 ℃.

The results are shown in Table 1.

TABLE 1

The inclusion of the adhesion promoter was found to have a significant effect on the thermal performance of the HMA formulation. The glass transition temperature (Tg) of the formulation was significantly higher compared to the reference HMA formulation.

In all four cases, Tc enthalpy appears to decrease; this may be due to the reduced amount of crystalline components and the effect of the adhesion promoter on the crystallization rate.

The inclusion of a tackifier was found to significantly reduce the viscosity or remain significantly the same.

Adhesive properties of HMA formulations

For the adhesion test, three types of paperboard were evaluated. General single board (WP 20/20) obtained by Smurfit Kappa and fromTwo kinds of cardboard (Frovi). HMA beads (melted at 163 ℃) were manually applied to the cardboard substrate with a glass rod, providing 1.5 to 2.5mm beads. A second paperboard substrate was applied to the bead to form an adhesive. The adhesive was pulled apart at an angle of almost 180 ° to break the adhesive 1 day and 4 days after bonding. Each sample was evaluated by recording the percentage of binder covered by fiberPercent fiber tear of (c).

The results of the adhesion test are shown in table 2.

TABLE 2

The results in table 2 show that the HMA formulations with the sorbitol and melamine initiated lactic acid oligomer tackifier resins (HMA 1, HMA 2, and HMA 3) have improved adhesion to almost all substrates compared to the reference and comparative examples. The reference and comparative HMA 1 formulations performed significantly worse after 4 days, indicating that the addition of the sorbitol lactic acid oligomer tackifier to HMA 1, HMA 2 and HMA 3 improves long-term adhesion.

Peel adhesion failure temperature

For most of the above HMA formulations, the Peel Adhesion Failure Temperature (PAFT) was determined.

The PAFT test was performed as follows:

HMA beads (melted at 163 ℃) were manually applied to the cardboard substrate with a glass rod, providing 1.5 to 2.5mm beads. A second paperboard substrate was applied to the beads to form a bond.

24 hours after the adhesive was made, it was hung and attached to the substrate with a 100g weight. When the substrate or adhesive failed at temperature, the weight dropped and the temperature was recorded.

The reference HMA showed PAFT over 90 ℃. The PAFT of HMA 1 exceeded 90 deg.C, the PAFT of HMA 2 was 52, and the PAFT of comparative HMA 1 exceeded 90 deg.C.

In view of the DSC and rheological properties of the HMA formulation, as well as the results of the adhesion and PAFT tests, HMA 1 was found to have better overall performance than HMA 2, but both HMA formulations were found to be superior to the reference and comparative formulations in most cases.

Effect of polyfunctional polymerization initiators on the Properties of oligomeric tackifiers

Several compounds having the same M were prepared_nAnd lactic acid content of tackifier, but with initiators of different functionality to investigate multifunctional polymerization initiationEffect of the agent on the performance of the tackifier.

Preparation of the tackifier lactic acid monomers derived from 100% L-lactide were used and different initiators as shown in table 3 were used as described in example 1 above.

Number average molecular weight (M) by GPC as described above_n). The enthalpy of fusion (J/g), glass transition temperature (Tg) and melting temperature (Tm) were determined by Differential Scanning Calorimetry (DSC) as described above.

The results are provided in table 3.

TABLE 3

Adhesive performance of HMAs with varying amounts of tackifier

As detailed in table 4, HMA formulations were prepared with varying amounts of the tackifier of example 1 to evaluate the effect of the amount of tackifier on the adhesive performance of the HMA formulations.

TABLE 4

The HMA formulation further comprises the same copolymer resin, oligomeric wax, and nucleating agent as described above for HMA 1 and HMA 2 formulations, and was prepared as follows. In a glass flask with overhead stirrer, the adhesion promoter was melted with stirring at a temperature of 163 ℃, and the nucleating agent was added to the melted adhesion promoter and mixed until melted and a homogeneous mixture was obtained. The oligomer wax was added and mixed until molten and a homogeneous mixture was obtained. Finally, the copolymer resin was added in small portions and mixed until molten and a homogeneous mixture was obtained. The mixture was kept at 163 ℃ with stirring until application. The adhesion of the different HMA formulations was tested on Frovi 250 cardboard. HMA beads (melted at 163 ℃) were manually applied to the cardboard substrate with a glass rod, providing 1.5 to 2.5mm beads. A second paperboard substrate was applied to the bead to form an adhesive. Subsequently, all test substrates were stored in duplicate at-20 ℃, 20 ℃ and 52 ℃ and tested for adhesion. The adhesive is pulled apart at an angle of almost 180 deg. to break the adhesive. The percent fiber tear for each sample was evaluated by recording the percentage of adhesive covered by fiber. Adhesion values are expressed as the perceived amount of fiber transferred to the applied adhesive after pulling the cardboard strip apart (% fiber tear).

The results are shown in tables 5, 6 and 7.

TABLE 5

TABLE 6

TABLE 7

The data show that adhesive retention is significantly improved by using tackifier resins at different temperatures. The optimum amount of tackifier will depend on the temperature of the end application.

The optimum amount of tackifier found to provide good adhesive properties at the start and over time over a wide range of temperatures (e.g., -20 ℃ to 52 ℃) is, for example, 15 to 35 wt%.