**4. Paper products from wheat straw pulps**

As previous discussed, bleached wheat straw pulps can be characterized with good strength properties, reasonable brightness, good printability, etc., which can be used to manufacture a wide range of paper and paperboard grades, such as light-weighted printing paper [16], letterpress printing paper, typing paper, writing paper, aluminum foil base paper, cylinder polished paper, tissue and sanitary papers, white board, coated ivory board, and almost all grades of paper and paperboard grades [17–22]. Practically, to improve pulp stock wet-web


twentieth century, China's wood pulp production from fast-grown woodchips by promotion of chemi-mechanical pulping technologies, such as CTMP (chemi-thermo-mechanical pulping), APMP (alkaline peroxide mechanical pulping), P-RC APMP (preconditioning-refiner chemical APMP), and CTMP-c (chemi-thermo-mechanical pulping with enhanced chemical

Chemi-mechanical pulping from wheat straw studies lasted for more than 30 years in China. In the early 1990s of the twentieth century, Liu and Fang [24] investigated chemi-mechanical pulping properties from wheat straw using caustic soda impregnation, characteristics of effluent, and proper treatment process. It was proven that wheat straw can be used to produce chemi-mechanical pulps using small amount of caustic soda with advantages as high pulp yield, good physical strength, and proper biodegradable effluents [25–27]. A-grade corrugated medium was produced from this kind of wheat straw CMP pulps (**Table 9**), and also A-grade

linerboard from WSCMP mixed with 15–30% kraft wood pulps was prepared [17, 24].

dosage and COD load versus pulp yield are illustrated in **Figures 5** and **6**.

**Specification GB1302 Corrugated medium from WSCMP (g/m2**

Breaking length (m) ≥4.30 4.94 4.71 Ring crush (N.m/g) ≥ 14.61 16.94

**Table 9.** Quality specifications of corrugated medium from wheat straw CMP pulps [17].

**Specific refining energy (kWh/t pulp)**

) 140 ± 2.0 140.3 180.6

) ≥0.5 0.56 0.61

**Bulk (cm3 /g)**

CTMP-1 3.0 78.9 827 3.23 19.5 1.04 4.23 2460 CTMP-2 4.0 75.5 555 2.66 32.6 1.60 4.56 3330 CTMP-3 5.0 73.1 336 2.35 41.3 2.31 4.08 4210

**Tensile (N.m/g)** **Burst (kPa. m2 /g)**

Grammage (g/m<sup>2</sup>

Density (g/cm3

**Pulp sample** **Caustic soda dosage (%)**

**Pulp yield (%)**

**Table 10.** CTMP pulping properties of wheat straw [28].

Zhang et al. [28] also investigated wheat straw chemi-mechanical pulping properties using two-stage caustic soda impregnation followed with two-stage atmospheric refining, while a total dosage of caustic soda 3–5% was applied at the impregnation stage, resulting pulp yield of 73.1% w/w–78.9% w/w, pulp tensile strength of 19.49–41.27 N.m/g, the specific refining energy consumption from 827 to 336 kWh/t pulp (**Table 10**), and COD load in effluent of 270.5–446.0 kg/t o.d. pulp (**Table 11**); the relationships between pulp yield versus caustic soda

**140 180**

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Wheat Straw Pulping for Paper and Paperboard Production

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**Tear (mN. m2 /g)**

**Breaking length (m)**

impregnation) processes, has increased rapidly [23].

**Table 7.** Portion of furnish for bible paper [18].


**Table 8.** Quality specification to bible paper products [18].

run ability in paper machine, wheat straw pulp furnishes must be mixed with some portion of bleached wood pulps or bamboo pulps occasionally [18, 20].

Some paper mills produce Bible paper products from bleached wheat straw pulps, the formula of pulp furnishes is given in **Table 7**, and the quality specifications of Bible paper are illustrated in **Table 8** [18].
