Wood Fibre Mat for Use as a Plant Substrate

Abstract

The present disclosure is directed to a wood fibre mat for use as a plant substrate including wood fibres, and at least one polar liquid absorbing agent, and a biodegradable binder consisting of polylactic acid fibres and at least one starch. The disclosure also relates to processes for its production.

Claims

1. A wood fiber mat for use as a plant substrate comprising wood fibers, and at least one polar liquid absorbing agent, further comprising: 5-10% by weight, based on the quantity of wood fibres, of a biodegradable binder of polylactic acid fibres and 5-10% by weight, based on the quantity of wood fibres, of at least one starch.

2. The wood fiber mat according to claim 1, wherein the at least one starch is selected from the group consisting of: potato starch, corn starch, wheat starch, and rice starch.

3. The wood fibre mat according to claim 1, wherein the at least one starch is present in native or modified form.

4. The wood fiber mat according to claim 1, wherein the at least one starch is a derivatized starch selected from the group consisting of: cationic or anionic starch, carboxylated starch, carboxymethylated starch, sulfated starch, phosphorylated starch, etherified starch, oxidized starch containing carboxyl or dialdehyde groups and hydrophobic starches.

5. The wood fibre mat according to claim 1, wherein the at least one starch is contained in an amount between 5 to 8% by weight, based on the amount of wood fibres (atro).

6. The wood fibre mat according to claim 1, wherein the polylactic acid fibres are contained in an amount between 5 to 8% by weight, based on the amount of wood fibres (atro).

7. The wood fibre mat according to claim 1, comprising a pH of more than 4.0

8. The wood fibre mat according to claim 1, wherein the at least one absorbent is an acrylic-based polymer.

9. The wood fibre mat according to claim 1, comprising at least one antimicrobial agent in an amount of between 0.5-5 wt %, based on the amount of wood fibres.

10. A plant substrate comprising the wood fibre mat according to claim 1.

11. A process for producing a wood fiber mat according to claim 1, comprising: (a) production of wood fibres from lignocellulosic raw material, (b) contacting the wood fibres with at least part of a solution of at least one starch, (c) drying of the wood fibres mixed with the at least one starch, (d) contacting the wood fibres mixed with the at least one starch with polylactic acid fibres, (e) applying the mixture of wood fibres, starch and polylactic acid fibres to a conveyor belt to form a fibre cake, and f) heating and compressing the fibre cake into a wood fibre mat.

12. The process according to claim 11, wherein at least a part of the solution of at least one starch together with the polylactic acid fibres is contacted with the wood fibres in step d).

13. The process according to claim 1, wherein in a step e1) the mixture of wood fibres, starch and polylactic acid fibres is applied to a first conveyor belt to form a pre-fleece and in a step e2) the pre-fleece is defibered and mixed and the fibre mixture is applied to a second conveyor belt to form a fibre cake.

14. The process according to claim 13, wherein at least one absorbent is applied to the pre-fleece and/or the fibre cake.

15. The process according to claim 13, wherein at least one antimicrobial agent is applied to the pre-fleece and/or the fibre cake.

16. The wood fibre mat according to claim 5, wherein the at least one starch is contained in an amount between 5 to 7% by weight, based on the amount of wood fibres (atro).

17. The wood fibre mat according to claim 6, wherein the polylactic acid fibres are contained in an amount between 5 to 7% by weight, based on the amount of wood fibres (atro).

18. The wood fibre mat according to claim 7, comprising a pH of more than 4.4.

19. The wood fibre mat according to claim 8, wherein the acrylic-based polymer comprises a co-polymer of acrylic acid and acrylate.

Description

Example 1

[0078] In a refiner, wood fibres are produced from wood chips, which are then mixed with a starch binder (Ecosynthetix) in the blowline. The added quantity was 5% by weight solid on wood atro. Different types of wood can be used, preferably softwood. The glue had a solids content of approx. 50%. This mixture was then dried to a moisture content of about 10%.

[0079] These wood fibres with starch binder are then mixed in a fibre mixer with polylactic acid fibres, (called PLA fibre) (proportion of polylactic acid fibres: approx. 5 wt % on wood fibres atro). The PLA fibres have a length of 38 mm +/3 mm and a fineness of 1.7 dtex.

[0080] An endless mat is produced from the mixture by blowing it onto a conveyor belt. Afterwards, the mat is mixed again and placed on another conveyor belt. Approx. 5600 g mixture/m.sup.2 are spread.

[0081] The fibre cake is then heated in a convection oven to temperatures of 120 -180 C. and calibrated to the desired thickness and thus compressed. During calibration, the fibre cake is cooled with cooling air to approx. 30-40 C. The production speed of the conveyor belt was 5 m/min. At the end of the circulating air oven the mat is compacted to 80 mm.

[0082] As a reference, a wood fibre mat with binding fibres based on PET (polyethylene terephthalate) of the same thickness and density (approx. 70 kg/m.sup.3) was produced. The proportion of binding fibres was approx. 7% by weight. The continuous fibre mat is used to produce cut-to-size or rolled products.

Example 2

[0083] In a refiner, wood fibres are produced from wood chips, which are then mixed with a starch binder (Ecosynthetix) in the blowline. The added quantity was 10% weight % solid on wood atro. The glue had a solids content of approx. 50%. This mixture was then dried to a moisture content of about 10%.

[0084] These wood fibres with starch binder are then mixed with polylactic acid fibres in a fibre mixer (proportion of polylactic acid fibres: approx. 3 wt % on wood fibres atro). The PLA fibres have a length of 22 mm +/3 mm and a fineness of 1.7 dtex.

[0085] A mat is produced from the mixture by blowing it onto a conveyor belt. Afterwards, the mat is mixed again and placed on a conveyor belt. Approx. 5600 g mixture/m.sup.2 are spread.

[0086] The fibre cake is then heated in a circulating air oven to temperatures of 120-180 C. and compressed. The speed of the conveyor belt was 5 m/min. At the end of the oven the mat is compacted to 80 mm. The endless fibre mat is used to produce cut-to-size or rolled products.

[0087] In addition to the pH value, the odour was also analysed on the samples. This was carried out by a group of people experienced in the olfactometric evaluation of products.

TABLE-US-00001 Zero sample Sample 1 Sample 2 pH value* 3.4 4.4 4.8 Odour Insulation material clearly acidic, Non-specific Non-specific after production vinegar-like *Amount of 1 g fibres were put into 50 ml distilled water, after approx. 10 minutes the pH value was determined

[0088] As can be seen from the table, insulating materials produced with starch and polylactic acid fibres have a significantly higher pH value, which is beneficial to plant growth.

Design example 3

[0089] In a refiner, wood fibres are produced from wood chips, which are then mixed with a starch binder (Ecosynthetix) in the blowline. The added quantity was 5% by weight solid on wood atro. Different types of wood can be used, preferably softwood. The glue had a solids content of approx. 50%. This mixture was then dried to a moisture content of about 10%.

[0090] These wood fibres with starch binder are then mixed in a fibre mixer with polylactic acid fibres, (called PLA fibre) (proportion of polylactic acid fibres: approx. 5 wt % on wood fibres atro). The PLA fibres have a length of 38 mm +/3 mm and a fineness of 1.7 dtex.

[0091] An endless mat is produced from the mixture by blowing it onto a conveyor belt. Afterwards, the mat is mixed again and placed on another conveyor belt. Approx. 5600 g mixture/m.sup.2 are spread.

[0092] The fibre cake is then heated in a convection oven to temperatures of 120-180 C. and calibrated to the desired thickness and thus compressed. During calibration, the fibre cake is cooled with cooling air to approx. 30-40 C. The production speed of the conveyor belt was 5 m/min. At the end of the circulating air oven the mat is compacted to 80 mm.

[0093] As a reference, a wood fibre mat with binding fibres based on polylactic acid fibres of the same thickness and density (approx. 70 kg/m.sup.3) was produced. The proportion of binding fibres was approx. 7% by weight. The continuous fibre mat is used to produce cut-to-size or rolled products. A sample was taken from the mat and stored in a desiccator above water. For comparison, the reference sample, which had only been prepared with polylactic acid, was also tested. It turned out that the reference sample or zero sample showed a clearly visible mould growth after about two months, whereas the test mat did not show this growth. In addition, a clearly earthy smell was noticeable when opening the desiccator. At best, this smell could be guessed when opening the desiccator with the test mat.